CA1267208A

CA1267208A - Message signaling arrangement between a switching system and user terminals

Info

Publication number: CA1267208A
Application number: CA000533467A
Authority: CA
Inventors: Leslie Alan Baxter; Barry Jay Weinbaum; James Robert Campbell; Gerald Steven Soloway; Wayne Alan Davidson; Nicholas Palumbo Palumbo; Robert Michael Lund; Ronald William Michelsen; Laura Marie Fandre
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1986-05-29
Filing date: 1987-03-31
Publication date: 1990-03-27
Anticipated expiration: 2007-03-27
Also published as: US4741026A

Abstract

A signaling arrangement where all terminal configuration data is stored in a switching system, but where each user terminal responds to a message from the system, defining one of the user terminal buttons as the selected call appearance at the terminal, by operating in a functional signaling mode to communicate with the system using functional messages concerning a call at the selected call appearance. Idle and ringing preference methods for use in terminating calls and auto-drop and auto-hold alternatives for use when moving from one call appearance to another are disclosed as well a methods for holding or dropping calls. Implicit and explicit conferencing methods are also disclosed.

Description

MESSAGE SIGNALING ARRANGEMENT BE~WEEN
A SWITCHING SYSTEM AND USER l'ER~INALS

Technical_Ei~l~

This invention relates to digital communication procedures and, moxe particularly, to message signaling protocols between digital telephone switching systems and associated customer station equipment.
~0~5~n~ Q5~ lsn One of the very important changes takiny place as digital technology is extended from digital switching systems to digital access lines serving fully digital user stations, is the replacement of traditional analog station signaling, involving~ for example, the transmission and detection of analog signals representing on-hook and off-hook states, by digital signaling procedures wherecomplete digital messages are exchanged to control calls.
Initially, such digital message signaling was of a type referred to as stimulus signaling where each message is either generated as a result of ~ ~ingle event at a user terminal or contains a basi~ instruction from the switzhing system to be executed by a user terminal.
Examples of such s~imulus messages include a message generated by a user t~rminal def ining the ac~ivation of a particular butto~, and a message from the switch, instructing a user terminaI to flash a given lamp. With stimulus ~ignaling, all the in~elligence giving mea~ing to the various user terminal events reside~ in the switch.
The switch processes stimulu~ messages deining button activations by reading stored data def ining, for example, that the activation o~ but~on number 8 at a given user terminal repre~ents a re~uest for a conference call or that button num~er 12 i6 a call appearance at the given terminal and its activation represents a preselection of :.~

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that call appearance by a user prior to initiating a call~
The activation of button number 8 and button number 12 at other user terminals may have completely different meanin~s. Placing all the intelligence concerning ~erminal configuration in the switch is desirable since all system users can be given identical terminals and the terminals can be configured in many ways to accommodate different u~er requirements.
Because of the incorporation of microprocessors in more sophisticated user terminal equipment, a second type of message signaling, reerred to as functional signaling, has evolved which involves a degree of intelligent processing in its generation or analysis.
With functional signaling, the switch and the user terminal communicate with each other as peers. The user terminal intelli~ence moves through a number of call states as the call progresses ~rom origination to disconnection. The messages generated in response to events at the user terminal are context-dependent, i.e., the message generated in response to a given event depends on the user terminal call state. With functional signaling, the user terminal knows the meaning of user events such as the activation of call appearance and feature buttons, and sends appropriate functional messages to the switch in response to such events. For example, when a particular call appearance is activa~ed at a user terminal that is off-hook and a destination directory number is subsequently entered, the user terminal may transmit a message requesting that the switch set up a call from the particular call appearance to the destination directory number. When a conference button is activated, the user terminal transmits a message requesting a conference call. The increased uqer terminal intelligence and the use of functional messages advantageously reduce the magnitude of call processing activity requlre~ of the switching system and facilitate the evolution of a wide variety of complex features.

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~owever~ functional signaling systems do not have the terminal configuration flexibility afforded when all terminal configuration data reside~ in the switch as with stimulus signaling systems. With functional signaling, each user terminal must be individually programmed such that the terminal knows the meaning of the particular configuration of buttons at that terminal.
In view of the foregoing, a recognized need in the art exists for a message signaling arrangement that allows intelligent peer-level communication between a switching system and user terminals without having to store data defininy terminal configuration in the individual terminals~

The aforementioned need is met and a technical advance is achieved in accordance with the principles of the invention in an exemplary signaling arrangement where all terminal configuration data is stored in the switch, but where a user terminal responds to a message from the switch, defining one of the user terminal buttons a~vantageously as the selected call appearance at the terminal, by operating in a functional signaling mode to communicate with the switch using functional messages concerning a call at the selected call app~arance.
The method of the invention is used between a switching system and a user terminal in controlling calls to and from the terminal-. ~he terminal has a number of buttons and is operable in a stimulus signaling mode and a functional signalin~ mode. The system stores data defining at least one of the buttons as a call appearance.
In accordance with the method, tha terminal operates in the stimulus signaling mode to communicate with the system using stimulus messages. At some point, the system transmits a message to the terminal de~ining the at least one cal]. appearance button as the selected call appearance at the terminal. The terminal responds to the message by operating in the functional signaling mode to communicate ., , . . ;, ~ ..
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with the system using functional messages concerning a call at ~he selected call appearance.
In accordance with an illustrative method for initiating calls, a user terminal responds to an activation of one of its buttonR by transmitting a first message to the system defining the activated button. The system reads tored data to determine whether the activated button is a call appearance. Upon determining that the activated button is a call appearance, the system transmits a second message to the terminal defining the activated button as the selected call appearance at the terminal. In response to the second message, the terminal and the system exchange functional messages to initiate a call rom the selected oall appearance~
lS Calls can be terminated to a user terminal using either idle preference or ringing preference. With idle preference, the system responds to an incoming call by determining two idle call appearances and informing the terminal tha~ the first determined appearance is the d~stination appearance and that the second determined appearance is the selected call appearance at the terminal. When the terminal subsequently goes off-hook, an outgoing call is initiated from the selected call appearance. Idle preference can be overridden if the first determined appearance button is activated before the terminal ~oes o~f-hook. The terminal transmits a stimulus message to the system defining the activated button. The system responds by readiny stored data to determine whether the activated button is a call appearance. Upon determining that the activated button is a call appearance, the system transmits a stimulus message to the terminal acknowledging that the call is held and defining the activated button as the selected call appearance at the terminal. When the terminal subsequently goes off-hook, the terminal and the system exchange functionalme sages to terminate the call to the selected call appearanceO

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With ringing preference, the system only determines one idle call appearance in response to an incoming call and informs the terminal that the determined appearance is both the destination appearanca and the selected call appearance at the terminal. When the terminal subsequently goes oCf-hook~ the terminal and the system exchange functional messages to terminate the call to the selected call appearance~
When a terminal is off-hook and a call appearance button is active on a first call and is the selected call appearance at the terminal, the activation of a second call appearance ~utton can result in the fir~t call either being dropped or held. In the auto-drop alternative, the terminal responds to the activation of the second button by transmitting a first message to the system defining the activated button. The system responds by reading stored data ts determine whether the activated button is a call appearance. Upon determining that the activated button is a call appearance, the system and the terminal exchange functional messages to disconnect the first call including a second message transmitted from the sy tem to the terminal defining the activated button as the selected call appearance at the terminal~ In response to the second message, the terminal and the system exchange functional messages to initiate a second call ~rom the ~elected call appearance defined by the second message. With the auto-hold alternative~ functional messages are exchanged to place the first call on hold rather than disconnecting it.
When the terminal is off-hook and a call appearance is active on a call and is selected at the terminal, the system responds to a ~ar-end disconnection of the call by exchanging functional messages with the terminal to disconnect the call at the selected call appearance including a first message transmitted from the sy~tem to the terminal defining that none of the call appearances is selected at the terminal. The terminal .
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responds to the first message and to an on-hook condition by transmitting a second message to the system defininq the on-hook condition. The system responds to the second message by reading stored data to determine an idle one of the call appearance~. The system then transmits a thixd message to the terminal def ining the determined idle call appearance as the selected call appearance at the terminal.
When the terminal is off hook and a call appearance is active on a call and is selected at the terminal, the terminal responds to an on-hook condition of the terminal by transmitting a first functional message to the system to disconnect the call. The system responds by reading stored data to determine an idle call appearance.
The system and the terminal exchange ~unctional messages to complete the disconnection of the call including a second functional message transmitted ~rom the system to the terminal defining the determined idle call appearance as the selected call appearance at the terminal.
When the terminal is off-hook and a call appearance is active on a call and is selected at the terminal~ the terminal responds to an activation of a HOLD
button by transmitting a first functional message to the system requesting that the call be placed on hold. ~he ~ystem transmits a second f unctional mes~age to the terminal acknowledging that the call is held and defining that none of the call appearances is selected at the terminal. The terminal responds tv an activation of the previously active call appearance button hy transmitting a first stimulus message to the system defining the activated button. The system reads stored data to determine-whether the activated button is a call appearance. Vpon determining that the activated button is a call appearance, the system transmits a second stimulus 3~ message to the terminal defining the activated button as the selected call appearance at the terminal. In response to the second stimulus message, the terminal and the ~. .

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system exchan~e functional messages to reconnect the call.
When the terminal is off-hook and a call appearance is active on a first call and is selected at the terminal, the terminal responds to an activation of a DROP button by transmitting a first functional message to the system requesting that the first call be dropped. The system xesponds to the first functional message by reading stored data to determine an idle call appearance. (The idle call appearance may be the call appearance for the call being dropped.) The system and the terminal exchange functional messages to disconnect the first call including a second functional message from the system to the terminal deining the idle call appearan~e as the selected call appearance at the terminal. In response to the second functional message, the terminal and the system exchange functional messages to initiate a ~econd call from the selected call appearance defined by the second functional message.
Two types of conference signaling referred to as implicit conferencing and explicit conferencing are described herein. When the terminal is off-hook and a call appearance is active on a first call and is selected at the terminal, for implicit conferencing the terminal responds to an activation of a CONFERENC~, button by tran~mitting a first functional message to the system requesting a conference. The system respondq to the first fllnctional message by placing the fir~t aall on hold and reading stored data to determine an idle call appearance.
The system transmits a second functional message to the terminal defining the determined idle call appearance as the selected call appearance for the second leg of the conference. In response to the second unctional message, the terminal and the system exchange functional messages to origina~e a second call from the determined call appearance. Once the second origination has been compl~ted, the terminal re~ponds to a second activation of the CONFER~NCE button by exchanging functional messages . .

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with the system to merge the first and second calls to form the conference. The system also transmits functional messages to the terminal to disconnect the call at the other call appearance.
With explicit conferencing, the terminal responds to an activation of the E30LD button by transmitting a first functional message to the system requesting that the first call be placed on hold. The system responds by placing the f irst call on hold and transmitting a s~cond functional message to the terminal defining that none of the call appearances is selected at the terminal. The terminal responds to the second functional message and to an ativation of a second call appearance but~on by transmitting a first stimulus me~sage to the system defining the activated button. The system responds to the first stimulus message by reading stored data to determine whether the activated button is an idle call appearance. Upon determining that the activated button is an idle call appearance, the system transmits a second ~timulus message to the terminal defining the activated button as the selected call appearance at the terminal. The terminal responds to the second stimulus message by exchangin~ functional messages with the system to originate a second call from the selected call appearance defined by the second stimulus me~sage. Once ~he second call origination has been completed, the terminal responds to an activation of the ~O~FERENCE
button by exchanging functional messages with the system to merge the f irst and second calls to form a conference~
The system al~o transmits functional messages to the terminal to disconnoct the call at the other call appearance .
es~rip~LQn~ioo A more complete understanding of the invention may be obtained from a consideration of the following description when r~ad in conjunc~ion with the drawing in which:

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FIGS. 1 through 3 illustrate the signaling method of the invention for use between a switching system and a user terminal, where the user terminal is initially in a stimulus signaling mode and then responds to a S message defining one of its buttons as the selected cal appearance at the terminal by operating in a functional signaling mode to communicate with the system concerning a call at the selected call appearance;
FIG. 4 is a more detailed diagram of the user terminal shown in FIGS~ 1 through 3;
FIG~ 5 is a diagram of an illustrative configuration of an ISDN switch and two exemplary ISDN
terminals wherein the signaling method of the present invention may be used;
FIG. 6 is a diagram of a memory included in the switch of FIG. 5;
FIG. 7 is a message 6equence diagram for a prior art functiollal signaling method;
FIGS. 8 through 20 are mes~age sequence diagrams for various illustrative call scenarios involving message signaling in accordance with the invention; and FI~. 21 i a diagram of the messa~e format used for the illustrative signaling method of the invention.
~il_n The principles of the present invention are ~escribed in the context of an integrated services digital network (ISDN) swit~h lOOQ tFIG. 5). An integrated services aigital network is defined as a network e~olved from the telephony integrated digital network that : 30 provides end-to-end digital connectivity to support a wide range of ~ervices, including voice and non~voice services, to which users have access by a limited set of standard multipurpose customer interacasl Howeve-r the invention is also applicable where swit~.h 1000 repre~ents an interconnected network o switching sy~tems. Switch 1000 : includes a switching network 1010, which repre~ents, in : the above-referencad exemplary integrated packet switching ... .

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and circuit switching system, a plurality o~ time-slot interchange units and a time~multiplexed switch to provide circuit~switched onnections, and a plurality of packet switching units (interconnected via the time-slot interchange units and time multiplexed switch) to provide packet-switched connections. Switch 1000 further includes control arrangement 1020 which represents the control portio~ of the above-referenced exemplary switching system, including a central control and a plurality of control units that intercommunicate via predetermined channels of the time-multiplexed switch and a control distribution u~it.
Also shown in FIG. 5 are two ISDN user terminals 1030 and 1040 which are connected to switch 1000 v~a associated user access lines (digital subscriber lines) 1031 and 1041. Although only two such terminals are explicitly shown, it is understood that æwitch 1000 interconnects a larger plurality of ISDN terminals and may inter~onnect conventional analog station sets as well. As shown in FIG. 4~ ISDN user terminal 1030 includes a handset 1037, a telephone keypad 1033 and a display 1032 for visually displaying messages. Terminal 1030 also inclu~es 22 buttons BN#l through BN~18 and 1087 through 1090. In ac~ordance with the present example, buttons 1087 through 1090 ar~ only used for the HOLD, DROP, CONFERENCE a~d TRANS~ER functions ~he remaining buttons happen to be configured at terminal 1030 such that buttons BN~l through BN#6 are call appearances and buttons BN#7 ~through ~#18 are feature buttons. Significantly7 the identical terminal could be configured to meet different user requirements such that buttons BN~l and BN#2 are call appearances~and buttons BN#3 through BN~6 and B~#7 through BN#18 are feature buttons or such that buttons BN~l throu~h BN~6 and BN~7 through BN#15 are feature buttons and buttons BN#16 through BN#18 are call appearances~
Each call appearance or feature button has as~ociated in-use and status lamps. For ~xample, button BN#l has , associated in-use lamp 1038 and status lamp 1039. The in-use lamp is lit for a call appearance when that call appearance is the selected call appearance at the terminal. ~he status lamp is used to indicate the various stages of calls, e.g., alerting, active, etc., or to indicate the activation of feature buttons.
Each ISD~ user terminal, e.~., 1030, transmits information to and receives information from switch 1000 (FIG. 5) in two 64 kilobits per second channels referred to as B-channels and in one 16 kilobits per second channel referred to as a D-channel. In the present embodiment, one B-channel is used to convey digitized voice samples at the rate of 8000 r eight-bit samples per second and the other B-channel is used to convey data at a rate of 64 kilobits per second. (However, each B-channel could be used for either voi e or data traffic.) Each B-channel is separately circuit-switched by switching network 1010 to other station equipment (either ISDN or analog). The D-channel is used both to convey signaling packets to effect message signaling between ISDN user terminals and control arrangement 1020, and to convey data packets between different ISDN user terminals. The D-channel is packet-switched by switching netwGrk 1010 either to other ISD~
uæer terminals, or to control arrangement 1020 which controls the establishment of both circuit-switched calls and packet~switched calls within switch 1000.
In the present exemplary embodiment, information is conveyed between an ISDN user terminal, e.q., 1030, and switching arrangement 1000 via a four-wire, user access line 1031 using one pair of wires for each direction of transmission. User access line 1031 transmits a serial bit stream at the rate of 192 kilobits per second which comprises 144 kilobits per second for the above-mentioned two 64 kilobits per second B-channels and one 16 kilobits per second D-channel and which further comprlses 48 kilobits per second used for a number of functions including framing, DC balancingr control and maintenance.

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User access line 1031 repre~ents what is referred to by the International Telegraph and Telephone Consultative Committee (CCITT) as the T-interface. The use of the T-interface is only exemplary, however, as the invention is equally applicable to systeme using other access methods.
Signaling packets are conveyed between the user terminals and control arrangement 1020 enclosed in level 2 (link-level) frames in accordance, for example, with the standard LAPD protocol. The exemplary signaling messages used for the control of circuit-switched voice calls are in accordance with CCIl'T Recommendation Q.931.
The message format is shown in FIG. 21. The protocol discriminator is the first octet of every message. For the present example, the protocol discriminator 00001000 is used to define basic circuit-switched ~circuit-mode) call control. The call reference typically comprises two octets coded as shown in FIG. 21.
The first octet defines the number of octets following the octet defining the length of the call reference.
Typically the first octet is coded as 00000001 indicating that only a single octet follows. The second oc~et includes the call reference and the call reference flag.
In some cases, a l-octet null call reference 00000000 is used. The purpose of the call reference is to define a particular call at the interface between the terminal and the switch. The third octet is used to define the message type. For example, the octet 00000001 defines an ALERTing message, the octet 01011010 defines a RELease COMPlete message and the octet 01111011 defines an INFOrmation message. The message type octet is followed by a number of information elements ~appropriate to the particular message type. Examples~of such information elements are the bearer capability~ call state, cause, channel identification, keypad, progress indicator~ ~witchhook, and ~elected call appearance information elements.

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The use of functional signaling messayes in accordance with the functional signaling method of the prior art is illustrated by con~idering the following example of a standard voice call from user terminal 1030 to user terminal 1040. Assume for the purposes of this example only that each user terminal stores its own terminal configuration data~ In accordance with the example, a user at terminal 1030 goes off-hook by lifting handset 1037. Terminal 1030 initially transmits a SETUP
message ~FIG. 7) to switch 1000. The SETUP message includes a call reference (CR) selected by terminal 1030.
The selected CR is included in all subse~uent siqnaling messages between terminal 1030 and switch 1000 concerning the particular call. Control arrangement 1020 of switch 1000 includes memory 3000 (FIG. 6), which may be implemented, for example, using a plurality of memories distributed throughout switch 1000, for storing both static and dynamic data needed for processing calls as well as a number of call processing programs. Control arrangement 1020 stores the received CR in a call record stored in a data table or relation in the dynamic data section of memory 3000. Switch 1000 then returns a S~TUP
ACK message tFIG~ 7) to terminal 1030. The user at terminal 1030 then enters via keypad 1033 the destination directory number and terminal 1030 transmits a sequence of INF0 messages each including one or more digits of the directory number. (Alternatively, all of the directory numbe~ ~igits may be included in the SETUP message.) Switch 1000 uses the recei~ed directory number as a key to : 30 translation data stored in memory 3000 and determines the identity of the terminating line 1041 for the call.
Switch I000 selects a CR for use in identifying the call : in the signaling messages to be conveyed between switch ~1000 and terminal 1040 and stores the selected CR in the call record of memory 3000. (Note that the CRs us~d for : ~ control communication with the ~riginating and terminating : terminals are in general different.) Switch 1000 also .

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reads network 1010 path data stored in memory 3000 and, if a network lDlC path is available to be assigned to the call, switch 1000 transmits a SETUP message informing tèrminal 1040 of the incoming call. The SETUP message includes calling party identity information, e.g., the directory number assigned to line 1031 or, alternatively the name of the calling party if such information is available to switch 1000. Terminal 1040 visually displays such calling party identity information on display 1042.
Switch 1000 also returns a CALL PROC message to station set 1030 indicating that a call is being set up in response to the received directory number. In response to the SET~P message, terminal 1040 enters an alerting state and begins ringing. Terminal 1040 then returns an ALERTING message to switch 1000, which message is also conveyed baek to originating terminal 1030. Subsequently when the handset is lifted to answer the call, terminal 1040 transmits a CO~NECT message ~o ~witch 1000, which effects the completion of the assigned network 1010 path and then transmits the CONNECT message on to terminal 1030. Switch 1000 also returns a CONNECT ACK message to terminal 1040. The two parties can now communicate.
The signaling method in accordance with the invention is illustrated herein by means of a number of exemplary call scenarios. The siynaling diagram associated with each scenario is shown in corresponding FIGS. 1 thr~ugh 3 and 6 through 18. The abbreviations used in the signaling d~agrams aro defined in Table 1.

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~ 15 -__._________.__ ___ _ _ _____. ___ _________ _ _ I BN# - Bu~ton Number CA - Call Appearance I CR - Call Reference 5 I DA Destination ~ppearance information element I OCR - Other Call Reference I FA - Feature Activation information element I OCA - Originati.on Call Appearance inormation elemen~ I
I SCA - Selected Call Appearance information element 10 I SWH - Switchhook information element ______ ____ __ ____ I
Table 1 As the irst example, consider that terminal 1030 is on hook and a user activates button BN~l. Since terminal 1030 does not store terminal configuration data, it does not know the meaning a~sociated with the activation of button BN~l. Terminal 1030 transmits an INFO message including the null call reference and a Feature Activation information element defining button BN#l to switch 1000 (FIG. 1). At this pointr terminal 1030 is operating in the stimulus signaling mode and the INFO message tranæmitted by terminal 1030 defining button BN~l is a stimulus message. Switch 1000 reads the terminal configuration data stored in memory 3000 and determines that button BN~l is a call appearance on terminal 1030. Switch 1000 returns an INFO message to terminal 1030 including the null call reference and a selected call appearance information element defining that button BN#l is a call appearance and is selected on .terminal 1030 (FIG. 2). In response to the selected call appearance, terminal 1030 begins operatlng in the ~: : functional signaling mode with respect to that call appearance. Terminal 1030 maintains at least ~our possible call states (Null, Alerting, Active and Held) for the call appearance and controls a traversal through the call states as a call from the sele~ted.call appearance progresses. When terminal 1030 sub~equently goes off-hook, terminal 1030 transmits a SET~P message to switch , .. ~: . . ..

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I Alerting COMN
I Active Not applicablel ¦ Held RECONN -¦
Table 2 Switch 1000 returns a SETUP ACK message to terminal 1030 and switch 1000 and terminal 1030 subsequently communicate using unctional messages to initiate a call from call appearance CAl in the manner shown in FIG. 7~
Next assume that an incoming call is received by switch 1000 and that switch 1000 reads the translation data and terminal busy~idle data stored in memory 3000 to determine that the call is to be completed to terminal 1030 and that call appearances CAl and CA2 are both idle at termi~al 1030 ~FIG. 8). Switch 1000 transmits a SETUP
message to terminal 1030 with information elements defining call reference 105 selected by switch 1~00, defining button BN#l as the destination call appearance for the incoming call, and defining button BN~ a~ an idle selected call appearance. In response, call appearance CAl begins alerting as indicated by the flashing of the status lamp and terminal 1030 returns an ALERT message to switch 1000. However, call appearance CA2 is the presently selected call appearance at terminal 1030 as indicated by the lighting of the in-use lamp.
Accordingly, call appearance CA2 is in the Null state.
When terminal 1030 subsequently goes of-hook, it .
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transmits a SETUP me s~ge to 6witch 1000 including information elements defining a call reference 3 ~elected by terminal 1030, defining call appearance CA2 a6 the originating call appearance for a call, and defining the off-hook Btatus of terminal 1030. Switch 1000 returns a S~TUP ACK me6sage to terminal 1030 and switch 1000 and terminal 1030 subsequently communicate usjng functional me~sages to initiate a call from call appearance CA2 in the manner shown in FIG. 7. The scenario just described is referred to: as idl~ p:re-fere~ce ~ since ~Jen when ~erminal 1030 is instructed to begin alerting at a call appearance for an incoming call, a second appearance i~
selected such that a user that subse~uently goes off-hook can initiate a call from the second call appearance.
The next example illu~trates the manner in which idle preference can be overridden to answer the incominq call. Just a6 before, switch 1000 transmits a SETUP
message to terminal 1030 with information elements defining call reference 105 selected by switch 1~00, defining button BN#l as the de~tinatlon call appearance Por the incoming call, and defining button BN#2 as an idle ~elected call appearance (FIGo 9)~ In re~pon-se, call appearance CAl begins alerting as indicated by the flashing of the status lamp and terminal 1030 returns an A~ERT message to ~witch lOQ0. However call appearance CA2 i8 the presently seIected call appearance at terminal 1030 as indicated by the lighting of the in-use lamp.
Accordingly, call appearance CA2 i8 in the Null ~tate. In this case, rather than going off-hook immediately as in FIG. 8, a user activates button BN~l at terminal 1030. At this point, terminal 1030 is in the stimulus signaling mode with respect to call appearance CAl 6ince it is not the selected call appearance~ Therefore terminal 1030 transmits a stimulu~ INF0 message to switch 1000 including information elements deining the null call reference and defining the activation of button BN~l. Switch 1000 reads the terminal configuration data for terminal 1030 ~tored : -~:

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The next signaling scenario pertains to the provision of ringing preference rather than idle preference. In this case, switch 1000 responds to the incomin~ call by transmitting a S~TUP message to terminal 1030 defining call reerence 105 and defi~ing button BN~l both as the destination appearance for the call and as the selected call appearance ~FIG. 10). In response, CAl ~egins alerting as indicated by the flashing of the status lamp and becomes the 0elected call appearance as indicated by the in-use lamp. With ringing preference, when terminal 1030 becomes off-hook it simply tran~mits a CONN
message to ~witch 1000 including information elements defining call reference lQ5 and the off-hook status of terminal 1030. Switch 1000 returns a CONN ACX message to terminal 1030 and completes the network connection.
When a particular call appearance is active and selected at a terminal, the activation of a second call appearance can result in the first call being dropped or alternatively, being placed on hold. The following scenarlo describes the auto-~rop alternative. Assume that terminal 1030 is off-hook and that call appearance CAl is active (with respect to a call having call reference 7) and selected (FIG. 11). At this pointy button BN#2 is activated at terminal 1030, ~erminal 1030 transmits a :-:
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-- lg --stimulus INFO message to switch 1000 def1ning the nul~
call reference and the activation of button BN~2. Switch 1000 reads the term1nal configuration data ~tored in memory 3000 for terminal 1030 and determines that BN~2 i6 S a call appearance~ ~ince terminal 1030 is active on call appearance CAl~ ~witch 1000 transmit~ DISC me~age defining call reference 7 to terminal 1030 and clears the existing call. In response to the DI~C me~sageS terminal returns a REL me~age to switch 1000. After the network is cleared, switch 1000 returns a REL COM message to terminal 1030 including information elements defining the call reference 7 and defining button BN~2 a~ the selected call appearance. Terminal 1030 can now operate in the functional signaling mode with re~pect to the selected call appearance CA2. Since terminal 1030 is off-hook and in the Null state with respect to call appearance CA2, terminal 1030 tran~mits a SETUP message to switch 1000 defining a new call reference 5 and defining call appearance CA2 as the oeiginating call appearance for the new call. 5witch 1000 return~ a SETUP ACK message to terminal 1030 and ~witch 1000 and terminal 1030 subsequently communicate using functional messages to initiate a call from call appearance CA2 in the manner ~hown in FIG. 7. In the auto-hold alternative, functional me66ages are exchanged to place tbe first call on hold, rather than dropping it.
The next example illustrates the signaling ~cenario when another terminal engaged in a call with terminal 1030 di~connect Terminal 1030 is off-hook and : 30 call appearance CAl is active (with respect to call reference 7) and selected (FIG. 12). Switch 1000 detects the far-end disconnection and transmits a DISC message to terminal 1030 defining call reference 7. Terminal 1030 and ~witch 1000 exchange REL and REL COM me ~ages as the 3S ne work connection is cleared. The REL COM me~sage transmitted by switch 1009 to terminal 1030 includes a null selected call appearance information element. In , ~
. . .
. . .~. .:: : ,.

, ~ , , - 20 - ~ ~ ~7,~

response, the in-use lamp associated with call appearance CAl is extinguished at terminal 1030. When terminal 1030 subsequently goes on-hook, terminal 1030 transmits a stimulus INFO message to SWitC~I 1000 defining the null call reference and the on-hook status of terminal 1030.
In response, switch 1000 reads memory 3000 to determine an idle call appearance, e.g., button BN#l, at terminal 10300 Switch 1000 includes a selected call appearance information element defining button BN#l in a stimulus INFO message transmitted to terminal 1030. In response the in-use lamp associated with call appearance CAl is again lit indicating that call appearance CAl is again selected at terminal 1030.
The signaling scenario when terminal 1030 disconnects from a call is shown in FIG~ 13. Terminal 1030 is off hook and call appearance CAl is active ~with respect to call reference 7~ and selected. At this point, terminal 1030 goes on-hook. Since call appearance CAl is the selected call appearance, terminal 1030 transmits the functional DISC message to switch 1000 defining call reference 7 and the on-hook state of terminal 1030.
Switch 1000 includes a selected call appearance information element defining button BN#l in the R~L
message returned to terminal 1030. hccordingly, the in-use lamp associated with CAl remains lit indicating thatcall appearance CAl is still the selected call appearance.
Call appearance CAl is in the ~ull state. Terminal 1030 then returns a REL COM message to switch 1 noo .
The use of the HOLD button BN#7 is illustrated ~y the ne~t signaling scenario. Assume that terminal 1030 is off-hook and that call appearance CAl is active (with respect to call reference 7~ and selected (~IG. 14). A
user at terminal 1030 activates the HOLD button BN#7.
Since terminal 1030 is in the functional signaling mode with respect to the selected call appearan~e CAl r terminal 1030 transmits a HOLD message defining call reference 7 to switch 10Q0. Switch 1000 returns a HOLD ACK message to terminal 1030 including a null selected call appearance information element. In response, terminal 1030 returns to the stimulus signaling mode with respect to call appearance CAl. The user at terminal 1030 then activat~s button BN~l and terminal 1030 responds by transmitting a stimulus INFO message to switch 1000 deflning a null call reference and defining the activation of button BN#l.
Switch 1000 reads the terminal configuration data for terminal 10~0 stored in memory 3000 and determines that button BN~l is a call appearance on terminal 1030. Switch 1000 returns an INFO message to terminal 1030 including the null call reference and a selected call appearance information element defining that button BN~l is a call appearance and is selected on terminal 1030. Since terminal 1030 is off-hook and call appearance CA1 is in the Held state, terminal 1030 responds to ~he call appearance selection by transmitting a RECONN message to switch 1000 defining call reference 7. Switsh 1000 removes the call from hold and returns a RECONN AC~
message to terminal 1030 defining call reference 7.
The use of the DROP button BN#8 is illustrated by the next two ignaling scenarios. First, assume that terminal 1030 is off hook and call appearance CAl is active (with respect to call r~ference 7) and selected (FIG. 15)~ Also assume that terminal 1030 is not the controller of a conference call. Since terminal 1030 is in the functional signaling mode with re~pect to the selected call appearance CAl, the activation of the DROP
button by a user a~ terminal 1030 results in the transmissiotl of a DROP message from terminal 1030 to switch 1000 defining call reference 7. Switch 1000 responds by clearing the network 1010 path used for th~
active call and returnin~ a DISC message to ter~inal 1030.
Terminal 1030 and switch 1000 then exchanqe REL and REL
COM messages. The REL COM message transmitted from switch ; 1000 to terminal 1030 includes a selected call appearance : information element defining calI appearance CAl as the .
, .. .

.

- 2~ 7~

selected call appearance. Accordingly, the in-use lamp associated with CAl remains lit indicating that call appearance CAl is still the selected call appearance, Call appearance CAl is in the Null state~ Since terminal 1030 is still off-hook, terminal 1030 transmits a functional SETUP message to switch 1030 defining a new call reference 13 and defining call appearance CAl as the originating call appearance. Switch 1000 returns a SETUP
ACK message to terminal 1030 and switch 1000 and terminal 1030 subsequently communicate using functional messages to initiate a call ~rom call appearance CAl in the manner shown in FIG. 7.
When terminal 1030 is the controller of a conference call, the activation of the DROP ~utton acts to drop the last added party to the conference. As before, assume that terminal 1030 is off-hook and call appearance CAl is active (with respect to call reference 7) and selected (FIG. 16). Since terminal 1030 is in ~he functional signaling mode with respect to the selected call appearance CAl~ the activation of the DROP button by a user at terminal 1030 results in the transmission of a DROP me sage from terminal 1030 to switch 1000 defining call reference 7O Switch 1000 responds by dropping the last party added to the conference and returning a DROP
: 25 ACK message to terminal 1030.
The remaining signaling scenarios deal with the establishment of con~erence calls. Assume again that terminal 103a is off-hook and that call appearance CAl is iactive (with respect to call reference 7) and selected.
Terminal 1030 is in the functional signaling mode with respect to call appeaxance CAl. Therefore, when a user at terminal 1030 activates the CON~ERENCE button BN#9, terminal 1030 transmits a CONF message to switch 1000 defining call reference 7~ Switch 1000 determines that this is the first activation of the CO~FERENCE button at terminal 1030 and acts to place call appearance CAl on hold. Switch 1000 also selects an idle call appearance at :`:

:.
.
~'. '' ~2~'7 terminal 1030 to be used for the second leg of the conference call. Switch 1000 includes the selected call appearance information element def ining call appearance C~2 in a HOLD ACK message returned to terminal 1030. The in~use lamp for call appearance CA2 is lit and call appearance CA2 is in the null state. Since terminal 1030 is of-hook and in the functional siynaling mode with respect to call appearance CA2, terminal 1030 transmits a functional SET~P message defining a new call reference 61 and defining call appearance CA2 as the originating call appear~nce. A standard origination occurs and when the second leg is completed, switch 1000 returns a CONN
message to terminal 1030 defining call reference 61. At this point r the user at terminal 1030 activates the CONFERENCE button 8N#9 for the second time and terminal 1030 transmits a CONF message to switch 1000 defining call reference 61. Switch 1000 responds to the receipt of tha second CONF message from terminal 1030 by completing a conference to the held call. Switch 1000 then transmits a CONF ACR message to terminal 103Q defining call reference 61 and also defining call reference 7 as the other call reference. Switch 1000 and terminal 1030 then exchange DISC, REL, and R~L COM messages to di~connect the second call from terminal 1030. The REL COM mes~age from switch 1000 includes a selected call appearance information element defining call appearance CAl as the new æelected call appearance at terminal 1030. Since call appearance CAl is in the HELD state, terminal 1030 responds to the R~L COM message by transmitting a R~CONN me~sage to switch 1000 defining the initial call reference. Switch 1000 responds with a RECONN A~K message. The conference procedure ~ust described is referred to as an implicit ~on~erence. The con~erence merger is effected to the held call. A ælightly different conference scenario is shown in FIG. 18 where the merger is effected to the aative call rather than the held call. Thus the held call (with call reference 7~ is discon~ected rather than the active call .

::.
` , ' .:, . ~.. ' - 24 ~ 8 (with call reference 61).
The next conference scenario is referxed to as explicit con~erencing and the signaling diagram is shown in FIG. 19. Again assume that terminal 1030 is initially o~f-hook with call appearance CAl active (with respect to call reference 7) and selected. In this scenario, a user at terminal 10~0 activates the HOLD button BN#7. Since terminal 1030 is in the functional signaling mode with respect to call appearance CAl, terminal 1030 transmits a ~OLD message to switch 1000 defining call reference 7.
Switch 1000 places call appearance CAl on hold and returns a ~OLD ACK message to terminal 1030 including a null selected call appearance information element. In response, ~erminal 1030 places call appearance CAl on hold, but since no call appearance is selected~ returns to the stimulus signaling mode. A user at terminal 1030 subsequently activates button BN#2. Terminal 1030 transmits a stimulus INFO message with inEormation elements defining the null call reerenoe and the activation of button BN#2. Switch 1000 reads the terminal configuration data stored in memory 3000 and determines that button BN~2 is a call appearance on terminal 1030.
Switch 1000 returns~an INFO message to terminal 1030 including the null call reference and a select~d call ~5 appearance information element defining that BN~2 is a call appearance and is selected on terminal 1030. In response to the selected calI appearance, terminal 1030 begins operatinq in the functional signaling mode with ~respect ~o that call appearance. Sin~e call appearance CA2 is in the Null state and terminal 1030 is off-hook, terminal 1030 transmits a unctionaI SETUP message to : ~ switch 1000 defining a new call reference 61 and defining : call appearance CA2 as ~he oriqinating call appearance. A
standard origination sequen~e ollows concluding with the transmission of a CONN message from switch 1000 to terminal 1030~ At this point, a user at terminal 1030 activates the CONFERE~CE button. In response, terminal ~.
..!
, ' ' ' '~ ~'' ', ~ '' ' , ' , 1030 transmits a CONF message to switch 1000 defininy the call reference 61 and also defining the other call reference 7~ Switch 1000 respond~ by completing the desired conference connection and ~hen returning a C~N~
ACK message to terminal 1030. Switch 1000 and terminal 1030 then exchange DISC, REL, and REL COM messages to disconnect the second call (having call reference 61) at terminal 1030. The REL COM message transmitted from switch 1000 to terminal 1030 includes a selected call appearance information element defining CAl as the selected call appearanceO Since call appearance CAl is in the Held state and terminal 1030 remains off-hook, terminal 1030 transmits a RECONN message to switch 1000 defining the original call reference 7. Switch 1000 responds with a RECONN ACX message to terminal 1030. FIG.
20 is the signaling diagram for a similar explicit conference scenaris except that rather than merging to the held call a~ in FIG. 19, the merger is effected to the current call. Note that with explicit conferer,cing, the terminal explicitly defines which call will be merged into the conference using the Other Call Reference (OCR) information element.
It is to be understood that the above-described signaling arrangement is merely illustrative of the principle of the present invention and that many variations ~,ay be devised by those skilled in the art without departing from the spirit and scope of the inventîon.

, '' ' ,

Claims

1. A signaling method for use between a switching system and a user terminal in controlling calls to and from said terminal, where said terminal has a plurality of buttons and is operable in a stimulus signaling mode and a functional signaling mode and said system stores data defining at least one of said buttons as a call appearance, said method comprising said terminal operating in said stimulus signaling mode to communicate with said system using stimulus messages, said system transmitting a message to said terminal defining said at least one button as the selected call appearance at said terminal and said terminal responding to said message by operating in said functional signaling mode to communicate with said system using functional messages concerning a call at said selected call appearance.

2. A method of initiating calls from one of a plurality of terminals served by a switching system, where each of said terminals has a plurality of buttons and said system includes memory means storing data defining for each of said terminals, certain ones of the buttons of that terminal as call appearances, said method comprising said one terminal, in response to an activation of one of the buttons of said one terminal, transmitting a first message to said system defining said activated button, said system reading said stored data in response to said first message to determine whether said activated button is a call appearance, upon determining that said activated button is a call appearance, said system transmitting a second message to said one terminal defining said activated button as the selected call appearance at said terminal, and in response to said second message, said one terminal and said system exchanging functional messages to initiate a call from said selected call appearance.

3. A signaling method for use between a switching system and a user terminal in controlling calls, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising said system, in response to an incoming call, reading said stored data to determine two idle ones of said call appearance buttons, said system transmitting a message to said terminal defining one of said determined call appearance buttons as the destination call appearance for said incoming call and defining the other one of said determined call appearance buttons as the selected call appearance at said terminal and said terminal responding to said message and to an off-hook condition of said terminal, by exchanging functional messages with said system to initiate an outgoing call from said selected call appearance.

4. A signaling method for use between a switching system and a user terminal in controlling calls, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising said system, in response to an incoming call, reading said stored data to determine two idle ones of said call appearance buttons, said system transmitting a first message to said terminal defining a first one of said determined call appearance buttons as the destination call appearance for said incoming call and defining a second one of said determined call appearance buttons as the selected call appearance at said terminal, said terminal responding to said first message and to an activation of said first determined call appearance button by transmitting a second message to said system defining said activated button, said system reading said stored data in response to said second message to determine whether said activated button is a call appearance, upon determining that said activated button is a call appearance, said system transmitting a third message to said terminal defining said activated button as the selected call appearance at said terminal and said terminal responding to said third message and to an off-hook condition of said terminal, by exchanging functional messages with said system to terminate said call to said selected call appearance defined by said third message.

5. A signaling method for use between a switching system and a user terminal in controlling calls, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising said system, in response to an incoming call, reading said stored data to determine an idle one of said call appearance buttons, said system transmitting a message to said terminal defining said determined call appearance button as the destination call appearance for said incoming call and as the selected call appearance at said terminal and said terminal responding to said message and to an off-hook condition of said terminal, by exchanging functional messages with said system to terminate said incoming call to said selected call appearance.

6. A signaling method for use between a switching system and a user terminal in controlling calls, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising the steps of:
A) when said terminal is off-hook and a first one of said call appearance buttons is selected at said terminal and is active on a first call, said terminal responding to an activation of a second one of said call appearance buttons by transmitting a first message to said system defining said activated button, B) said system reading said stored data in response to said first message to determine whether said activated button is a call appearance, C) upon determining that said activated button is a call appearance, said system transmitting a second message to said terminal defining said activated button as the selected call appearance at said terminal, and D) in response to said second message, said terminal and said system exchanging functional messages to initiate a second call from said selected call appearance defined by said second message.

7. A method in accordance with claim 6 wherein said step C) further comprises upon determining that said activated button is a call appearance, said system and said terminal exchanging functional messages to disconnect said first call.

8. A method in accordance with claim 6 wherein said step C) further comprises upon determining that said activated button is a call appearance, said system and said terminal exchanging functional messages to place said first call on hold.

9. A signaling method for use between a switching system and a user terminal in controlling calls, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising when said terminal is off-hook and one of said call appearance buttons is selected at said terminal and is active on a call, said system responding to a far-end disconnection of said call by exchanging functional messages with said terminal to disconnect said call at said selected call appearance including a first message transmitted from said system to said terminal defining that none of said call appearances is selected at said terminal, said terminal responding to said first message and to an on-hook condition of said terminal by transmitting a second message to said system defining said on-hook condition, said system responding to said second message by reading said stored data to determine an idle one of said call appearances and said system transmitting a third message to said terminal defining said determined idle call appearance as the selected call appearance at said terminal.

10. A signaling method for use between a switching system and a user terminal in controlling calls, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising when said terminal is off-hook and one of said call appearance buttons is selected at said terminal and is active on a call, said terminal responding to an on-hook condition of said terminal by transmitting a first functional message to said system to disconnect said call, said system responding to said first message by reading said stored data to determine an idle one of said call appearances t and said system and said terminal exchanging functional messages to complete the disconnection of said call including a second functional message transmitted from said system to said terminal defining said determined idle call appearance as the selected call appearance at said terminal.

11. A signaling method for use between a switching system and a user terminal in controlling calls, where said terminal has a plurality of buttons including a HOLD button and can assume on hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising when said terminal is off-hook and one of said call appearance buttons is selected at said terminal and is active on a call, said terminal responding to an activation of said HOLD button by transmitting a first functional message to said system requesting that said call be placed on hold, said system transmitting a second functional message to said terminal defining that none of said call appearances is selected at said terminal, said terminal responding to said second functional message and to an activation of said one call appearance button by transmitting a first stimulus message to said system defining said activated button, said system reading said stored data to determine whether said activated button is a call appearance, upon determining that said activated button is a call appearance, said system transmitting a second stimulus message to said terminal defining said activated button as the selected call appearance at said terminal and in response to said second stimulus message, said terminal and said switch exchanging functional messages to reconnect said call.

12. A signaling method for use between a switching system and a user terminal in controlling calls, where said terminal has a plurality of buttons including a DROP button and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising when said terminal is off-hook and one of said call appearance buttons is selected at said terminal and is active on a first call, said terminal responding to an activation of said DROP button by transmitting a first functional message to said system requesting that said first call be dropped, said system responding to said first functional message by reading said stored data to determine an idle call appearance, said system and said terminal exchanging functional messages to disconnect said first call including a second functional message from said system to said terminal defining said idle call appearance as the selected call appearance at said terminal and in response to said second functional message, said terminal and said system exchanging functional messages to initiate a second call from said selected call appearance defined by said second functional message.

13. A signaling method for use between a switching system and a user terminal in controlling calls, where said terminal has a plurality of buttons including a CONFERENCE button and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising when said terminal is off-hook and one of said call appearance buttons is selected at said terminal and is active on a first call, said terminal responding to an activation of said CONFERENCE button by transmitting a first functional message to said system requesting a conference, said system responding to said first functional message by placing said first call on hold and reading said stored data to determine an idle one of said call appearances, said system transmitting a second functional message to said terminal defining said determined call appearance as the selected call appearance for the second leg of said conference, in response to said said second functional message, said terminal and said system exchanging functional messages to originate a second call from said determined call appearance and once said second call origination has been completed, said terminal responding to a second activation of said CONFERENCE button by exchanging functional messages with said system to merge said first and second calls to form said conference.

14. A signaling method for use between a switching system and a user terminal in controlling calls, where said terminal has a plurality of buttons including a HOLD button and a CONFERENCE button and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising when said terminal is off-hook and a first one of said call appearance buttons is selected at said terminal and is active on a first call, said terminal responding to an activation of said HOLD button by transmitting a first functional message to said system requesting that said first call be placed on hold, said system responding to said first functional message by placing said first call on hold and transmitting a second functional message to said terminal defining that none of said call appearances is selected at said terminal, said terminal responding to said second functional message and to an activation of a second one of said call appearance buttons by transmitting a first stimulus message to said system defining said activated button, said system responding to said first stimulus message by reading said stored data to determine whether said activated button is an idle call appearance, upon determining that said activated button is an idle call appearance, said system transmitting a second stimulus message to said terminal defining said activated button as the selected call appearance at said terminal, said terminal responding to said second stimulus message by exchanging functional messages with said system to originate a second call from said selected call appearance defined by said second stimulus message, once said second call origination has been completed, said terminal responding to an activation of said CONFERENCE button by exchanging functional messages with said system to merge said first and second calls to form a conference.

15. A signaling method for use by a user terminal served by a switching system, where said terminal has a plurality of buttons, said method comprising in response to an activation of one of said buttons, transmitting a first message to said system defining said activated button, receiving a second message defining said activated button as the selected call appearance at said terminal, and in response to said second message, transmitting a functional message to said system to initiate a call from said selected call appearance.

16. A signaling method for use by a switching system serving a user terminal having a plurality of buttons, where said system includes memory means storing data defining certains ones of said buttons as call appearances, said method comprising receiving a first message from said terminal defining an activated one of said buttons, reading said stored data in response to said first message to determine whether said activated button is a call appearance, upon determining that said activated button is a call appearance, transmitting a second message to said terminal defining said activated button as the selected call appearance at said terminal, and receiving a functional message from said terminal defining the initiation of a call from said selected call appearance.

17. A user terminal for use with a switching system, said terminal comprising a plurality of buttons, means responsive to an activation of one of said buttons for transmitting a first message to said system defining said activated button, means for receiving a second message defining said activated button as the selected call appearance at said terminal, and means responsive to said second message for transmitting to said system a functional message to initiate a call from said selected call appearance.

18. A switching system serving a user terminal having a plurality of buttons comprising memory means storing data defining certain ones of said buttons as call appearances, means for receiving a first message from said terminal defining an activated one of said buttons, means for reading said stored data in response to said first message to determine whether said activated button is a call appearance, means responsive to a determination that said activated button is a call appearance for transmitting a second message to said terminal defining said activated button as the selected call appearance at said terminal and, means for receiving a functional message from said terminal defining the initiation of a call from said selected call appearance.

19. A signaling method for use by a user terminal in controlling calls to and from a switching system, where said terminal has a plurality of buttons and is operable in a stimulus signaling mode and a functional signaling mode and where said system stores data defining at least one of said buttons as call appearance, said method comprising operating in said stimulus mode to communicate with said system using stimulus messages, receiving a message from said system defining said at least one button as the selected call appearance at said terminal and responding to said message by operating in said functional signaling mode to communicate with said system using functional messages concerning a call at said selected call appearance.

20. A signaling method for use by a user terminal in controlling calls to and from a switching system, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising receiving a message from said switching system defining one of said buttons as the destination call appearance for an incoming call and defining another one of said buttons as the selected call appearance at said terminal and responding to said message and to an off-hook condition of said terminal by sending a functional message to said system to initiate an outgoing call from said selected call appearance.

21. A signaling method for use by a user terminal in controlling calls to and from a switching system, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising receiving a message from said system defining one of said buttons as the destination call appearance for an incoming call and as the selected call appearance at said terminal and responding to said message and to an off-hook condition of said terminal by sending a functional message to said system to terminate said incoming call to said selected call appearance.

22. A signaling method for use by a user terminal in controlling calls to and from a switching system, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising responding, when said terminal is off-hook and a first one of said call appearance buttons is selected at said terminal and is active on a first call, to an activation of a second one of said call appearance buttons by transmitting a first message to said system defining said activated button, receiving a second message from said switching system defining said activated button as the selected call appearance at said terminal, and in response to said second message, sending a functional message to initiate a second call from said selected call appearance defined by said second message.

23. A method in accordance with claim 22 wherein said method further comprises after transmitting said first message and before receiving said second message, receiving a message from said switching system to disconnect said first call.

24. A method in accordance with claim 22 wherein said method further comprises after transmitting said first message and before receiving said second message, receiving a message from said switching system to place said first call on hold.

25. A signaling method for use by a switching system in controlling calls to and from a user terminal, where said terminal has a plurality of buttons and is operable in a stimulus signaling mode and a functional signaling mode and said system stores data defining at least one of said buttons as a call appearance, said method comprising receiving a stimulus signaling message from said terminal, transmitting a message to said terminal defining said at least one button as the selected call appearance at said terminal and after said transmitting step, receiving from said terminal a functional signaling message concerning a call at said call appearance.

26. A signaling method for use by a switching system in controlling calls to and from a user terminal, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as a call appearance and defining the busy/idle status of said call appearance, said method comprising reading said stored data, in response to an incoming call, to determine two idle ones of said call appearance buttons, transmitting a message from said terminal defining one of said determined call appearance buttons as the destination call appearance for said incoming call and defining the other one of said determined call appearance buttons as the selected call appearance at said terminal and after said transmitting step, receiving a functional message from said terminal to initiate an outgoing call from said selected call appearance.

27. A signaling method for use by a switching system in controlling calls to and from a user terminal, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising reading said stored data, in response to an incoming call, to determine an idle one of said call appearance buttons, transmitting a message to said terminal defining said determined call appearance button as the destination call appearance for said incoming call and as the selected call appearance at said terminal and after said transmitting step, receiving a functional message from said terminal to terminate an incoming call to said selected call appearance.

28. A signaling method for use by a switching system in controlling calls to and from a user terminal, where said terminal has a plurality of buttons and can assume on-hook and off-hook conditions and where said system stores data defining certain ones of said buttons as call appearances and defining the busy/idle status of said call appearances, said method comprising the steps of:
(A) when said terminal is off-hook and a first one of said call appearance buttons is selected at said terminal and is active on a first call, said system receiving a first message from said terminal defining the activation of a second one of said call appearance buttons, (B) said system reading said stored data in response to said first message to determine whether said activated button is a call appearance, (C) upon determining that said activated button is a call appearance, said system transmitting a second message to said terminal defining said activated button as the selected call appearance at said terminal, and (D) after step (C), said system receiving a functional message from said terminal, to initiate a second call from said selected call appearance defined by said second message.

29. A method in accordance with claim 22 wherein step (C) further comprises upon determining that said activated button is a call appearance, said system sending a functional message to said terminal to disconnect said first call.

30. A method in accordance with claim 28 wherein step (C) further comprises upon determing that said activated button is a call appearance, said system sending a functional message to said terminal to place said first call on hold.