WO1997039559A1

WO1997039559A1 - Method and equipment for controlling transfer of calling line identity

Info

Publication number: WO1997039559A1
Application number: PCT/SE1997/000632
Authority: WO
Inventors: Gunnar Olsson
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 1996-04-16
Filing date: 1997-04-15
Publication date: 1997-10-23
Also published as: SE9601443L; SE9601443D0; AU2419797A

Abstract

A method and an equipment are disclosed, for controlling transfer of CLI (Calling Line Identity) between a calling subscriber terminal (1), connected to a first local exchange (21), and a called subscriber terminal (2), connected to a second local exchange (22), across a speech path between said terminals. The CLI is requested using an in-band request signal, and the CLI is transmitted when a talking connection has been established. The equipment comprises subscriber category means (26) related to the called terminal (2), checking whether the called subscriber terminal (2) has a valid subscription to the service of receiving the CLI and control means (28), controlling the transmission of the CLI to the called terminal (2) in dependence of the subscriber category of the called terminal (2).

Description

METHOD AND EQUIPMENT FOR CONTROLLING TRANSFER OF CALLING LINE IDENTITY

This invention relates to a method and a device for controlling CLIP (Calling Line Identity Presentation) in telecommunication systems.

Technical Field of the Invention

The invention relates to controlling transmission of a CLI (Calling Line Identity) within any telephone network wherein a plurality of subscriber terminals are linked to at least one exchange having switching circuitry for establishing talking connec¬ tions between calling and called terminals. In particular, the invention relates to older types of telephone systems where transmission of a CLI is not possible during the set-up phase ofthe call.

Description of Related Art

Knowledge of CLI is particularly useful to emergency personnel such as the police, fire or ambulance services. However, there is sometimes a wish to offer a CLIP (Calling Line Identity Presentation) service to residential subscribers, and check before presenting the CLI whether or not a called subscriber has paid the CLIP subscription. This means a need for a CLIP prevention facility.

In modern telecommunication systems, the transmission of CLI is made during the connection phase of a call, i.e. before establishing the speech path connection. A system of that kind is described for instance in US 4,754,475, which discloses a method and a device for identification of a calling telephone terminal from the tele¬ phone network. An mcoπiing telephone exchange serving a called telephone exchange is programmed to initiate a process for identifying the calling telephone terminal, and then allows the terminating telephone exchange to complete the identification process. According to US 4,754,475, the transmission of the CLI is made before establishing the speech path connection. In some older types of telephone systems, however, this is not possible.

US 4,445,001 describes a device and method for transmission of CLI, wherein an established talking connection is interrupted by a request generator, comprised in the local exchange ofthe called subscriber, which generator sends a trigger signal. A corresponding identity transmitter, comprised in the local exchange of the calling subscriber responds by sending the identity ofthe calling subscriber to be stored in the local exchange of the called subscriber, from where it may be sent to the called subscriber. In this disclosure it is suggested that, to make it possible to prevent use of the CLIP service, the signal emitted by the request generator could be, not the trigger signal itself but an activating signal with a frequency outside the voice band, the request generator itself being insertable in response to this activating signal into the established talking connection at a point downstream the associated identity trans¬ mitter, as seen from the called subscriber.

However, in a telephone system where the CLI request signal has a frequency within the voice band, the method described in US 4,445,001 cannot be used. The request generator could not distinguish between the request and speech signals in this case.

When the CLI request is sent as a tone signal in the speech channel after the called subscriber has lifted the handset, it is possible for the called subscriber to generate such a signal by means not comprised in the telephone network. In this way, subscribers who are not authorized to get CLI may get information that they are not entitled to, for example because they have not paid for it. Summary

It is an object of the present invention to provide a method and a device for enabling a telephone system operator to control presentation of CLI in accordance with a called subscriber category, the term category here referring to information concerning type of subscriber, rights of subscriber etc.

Another object of the invention is to provide a method and a device for preventing subscribers from receiving CLI if they are not permitted to do so.

Another object of the invention is to provide a low cost installation, which can be implemented without imposing any additional requirements on surrounding network, interconnected network operators or suppliers.

Another object of the present invention is to provide a method and a device for preventing subscribers from receiving CLI if they are not permitted to do so, in a telephone system where a CLI request signal, having a frequency within the voice band, is sent after the set-up phase of the call.

These objects are achieved by a method having the characterizing features in claim

1, and a device for performing the method is disclosed in claim 6. Further features and improvements ofthe invention, are given in the dependent claims.

According to the invention, prevention of CLIP to unauthorized users is achieved by a method and an equipment for controlling transfer of CLI (Calling Line Identity) between a calling subscriber teixninal, connected to a first local exchange, and a called subscriber teπninal, connected to a second local exchange, across a speech path between said terminals. The CLI is requested using an in-band request signal, and the CLI is transmitted when a talking connection has been established. The equipment comprises subscriber category means related to the called terminal, checking whether the called subscriber terminal has a valid subscription to the service of receiving the CLI and control means controlling the transmission of the CLI to the called terminal in dependence of the subscriber category of the called terminal.

Brief Description of the Drawings

For a more complete understanding of the present invention and for further objects and advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

fig 1 shows two subscriber terminals connected via a network;

fig 2 shows how CLI (Calling Line Identity) can be transmitted;

fig 3 shows how CLI transmission is controlled according to the invention; and

fig 4 shows how CLI transmission is controlled according to another embodiment ofthe invention.

Detailed Description of Embodiments

Fig 1 shows two subscriber terminals 1 and 2 connected via a network 3, in accordance with a preferred embodiment of the invention. A calling subscriber teπninal 1 is connected via a jack 4 to the network 3 having a plurality of connec- tions 5, and a called subscriber terminal 2 is connected to the network 3 via a jack 6. Both subscriber terminals 1,2 each comprise a CLI request means 7,10, a CLI receiver 8,11 and a display means 9, 12, which may be connected to the subscriber terminals 1,2 in any suitable way, well known in the art. The network 3 may comp- rise a plurality of subscriber terminals.

Fig 2 shows how CLI (Calling Line Identity) transmission may be controlled, according to the invention, when a phone call is made by a calling subscriber terminal 1 to a called subscriber terminal 2, having the system according to the in- vention installed. The calling subscriber terminal 1, having a phone number denoted

A-number, and the called subscriber terminal 2, having a phone number denoted B- number, are connected to a first local exchange 21 (called LE, below) and a second LE 22 via jacks 4, 6 respectively.

The first and second LE:s 21,22 are connected to a transit exchange 20 (called TE, below). The TE 20 may have a plurality of LE.s connected and the LE:s may have a plurality of subscriber terminals connected. The first and second LE:s 21,22 may also be directly interconnected, as indicated by the dotted line, thus omitting the TE 20. The first LE 21 comprises, in addition to the means conventionally comprised in an exchange well known in the art, a subscriber category means 25, a CLI control means 27 and a CLI sending means 31. The second LE 22 comprises, in addition to the means conventionally comprised in an exchange well known in the art, a subscriber category means 26, a CLI control means 28 and a CLI sending means 32. The means 25,27,31,26,28,32 comprised in the first and second LE:s 21,22 may be remote controlled using remote control means 33,34. The TE 20 is of a conventional type, well known in the art.

The subscriber category means 25, 26 are adapted to check subscriber category, i.e. to assess information concerning subscriber type, rights of subscriber etc. The subscriber category may comprise an authority to receive CLI. The CLI control means 27, 28 are adapted to control the transfer of CLI. According to a preferred embodiment of the invention, this is achieved by breaking the established speech path through the LE (21 or 22) to which the subscriber is connected who is to receive or not receive the CLI.

The CLI sending means 31, 32 are adapted to send CLI across an established speech connection.

When the hook is lifted at the calling subscriber terminal 1, an off-hook signal is sent to the LE 21. The dialled number, B-number, is sent to the first LE 21, from which a seizure signal is sent to the TE 20. The B-number is then sent to the TE 20, from where the seizure signal is forwarded to the second LE 22. The B-number is then forwarded to the second LE 22. Alternatively, both the seizure signal and the B- number could be sent directly from the first LE 21 to the second LE 22.

At this stage, through connection of speech path is accomplished. From the second LE 22 a ring signal is sent to the called subscriber terminal 2, and a ring tone to the calling subscriber terminal 1. Upon lifting the hook at the called subscriber terminal 2, an off-hook signal is sent to the second LE 22, from where an answer signal is sent to the TE 20 and forwarded to the first LE 21. The call has now been establis¬ hed between the terminals 1 and 2 in a way common in the art.

The originating node, i.e. the first LE 21, prepares for a possible in-band CLI- request by activating the CLI sending means 31 if certain criteria are fulfilled, in terms of originating code, destination code and type of calling subscriber. If the call is made by the operator, for instance, or if the call is international, the CLI sending means 31 may not be activated. These criteria may be evaluated by the subscriber category means 25, comprised in the first LE 21, or in any other way well known in the art. When the answer signal is received the speech path through the first LE 21 is broken in the direction towards the calling subscriber station 1 for a predetermined time adapted for CLI transfer and, instead ofthe calling subscriber terminal 1 the CLI sending means 31 comprised in the first LE 21, is connected for e.g. MFP-code (Pulsed Multi Frequency code). This break of speech path may be performed by the CLI control means 27 comprised in the first LE 21, or be provided in any other way, well known in the art.

At this stage, CLI may be requested, using a CLI request signal with a frequency within the voice band, for instance a 500 Hz tone, sent by the CLI request means 10, comprised in the called subscriber terminal 2, to the CLI sending means 31 comp¬ rised in the first LE 21, across the established speech path between the CLI sending means 31 and the called subscriber terminal 2. The CLI sending means 31 responds to the CLI request signal by sending, also over the speech path, the CLI, comprising for instance the A-number and where applicable an A-category, to the called subscriber terminal 2, where the CLI may be received by the CLI receiver 11, and presented using the display means 12.

The request for CLI is thus sent in-band (within the speech frequency band) with a CLI request signal after completion of the set-up phase of the call, and after the answer signal has been transmitted. The CLI request signal is applied by the CLI request means 10 immediately after inducing the answer signal by lifting the handset of the called subscriber terminal 2.

If the CLI request signal is detected by the CLI sending means 31 within a specified time, e.g. 250-1000 ms, the CLI sending means 31 responds by sending the CLI, and then the CLI sending means 31 is released and the speech path is restored. If the CLI request signal is not received within the stipulated time, the CLI sending means 31 is removed and the speech path is restored. Fig 3 shows how CLI transmission may be controlled, and if applicable prevented, according to the invention. Initially, the method is the same as in fig 2 up till the stage where the calling subscriber teixninal 1 has been disconnected and replaced by the CLI sending means 31. According to the invention, the subscriber category means 26, comprised in the second LE 22, checks a subscriber category (i. e. information concerning type of subscriber, rights of subscriber, valid subscriptions etc.) of the called subscriber 2, to find out whether or not the called subscriber 2 has paid for a subscription to the CLIP (Calling Line Identity Presentation) service and thus is authorized to receive the CLI that may be sent from the calling subscriber 1. If not, the CLI control means 28, comprised in the second LE 22, will break the established speech path through the second LE 22 for a predetermined time adapted to the duration of the transmission of CLI from the CLI sending means 31. If CLI is requested using a CLI request signal within the speech frequency band, e.g. 500 Hz, from the CLI request means 10, the request signal will be stopped in the second LE 22. After the predetermined time, i.e. when the CLI sending means 31 has been disconnected, the speech path between the subscriber terminals is restored. Since the specified time for CLI transfer is as short as for instance 250-1000 ms, the temporary break of speech path is of minor discomfort to the subscribers.

Thus, according to the invention, the CLI transmission is stopped if the called subscriber terminal 2 has not subscribed to the CLIP service. The CLI control means 28, comprised in the second LE 22, detects the off-hook signal from the called sub¬ scriber terminal 2 and orders a break of the speech path through the second LE 22, in both directions, or in the direction towards the calling subscriber terminal 1 only, for a specified length of time, about 1 second. This break ofthe speech path will prohibit the CLI request signal from reaching the CLI sending means 31, comprised in the first LE 21, and therefor no CLI will be sent.

Fig 4 shows how CLI transmission may be controlled and if applicable prevented according to another embodiment ofthe invention. The procedure is the same as in fig 3, but the speech path is broken through the second LE 22 in the direction to¬ wards the called subscriber terminal 2 only. The CLI request signal may be sent by the CLI request means 10, and received by the CLI sending means 31, but the CLI then sent will not reach the CLI receiver 11 as the speech path is broken in this direction for the time that the CLI sending means 31 is connected.

The CLI sending means 31 is connected for a predetermined time, e.g. 250-1000 ms, adapted for the transmission of the CLI. During this time the speech path is broken through the second LE 22 according to the invention if the called subscriber 2 does not have authority to receive CLI. The CLI sending means 31 will send the CLI upon receiving the CLI request signal regardless of the called subscribers 2 category concerning the CLIP service, but the called subscriber 2 will only receive the CLI if authorized to do so.

Claims

1. A method for controlling transfer of CLI ( Calling Line Identity ) between a calling subscriber terminal (1), connected to a first local exchange (21), and a called subscriber terminal (2), connected to a second local exchange (22), across a speech path between said terrninals, wherein the CLI is requested using an in-band request signal, and the CLI is transmitted when a talking connection has been established between the terminals (1 and 2), characterized by the following steps:

- checking whether the called subscriber terminal (2) has a valid subscription to the service of receiving the CLI; and

- providing the called subscriber terminal (2) with the CLI only if the check con¬ firms a valid subscription.

2. Method according to claim 1, characterized by further comprising breaking the speech path through the second local exchange temporarily during a predetermined time adapted to the CLI transfer operation, if the called subscriber is not authorized to receive CLI.

3. Method according to claim 2, characterized in that the speech path is broken in both directions through the second local exchange (22).

4. Method according to claim 2, characterized in that the speech path is broken in the direction towards the calling subscriber terminal (1) only.

5. Method according to claim 2, characterized in that the speech connection is broken in the direction towards the called subscriber terminal (2) only.

6. An equipment for controlling transfer of CLI between a calling subscriber terminal (1), connected to a first local exchange (21), and a called subscriber terminal (2), connected to a second local exchange (22), across a speech path between said terminals, wherein the CLI is requested using an in-band request signal, and the CLI is transmitted when a talking connection has been established, characterized by

- subscriber category means (26) related to the called subscriber terminal (2), checking whether the called subscriber terminal (2) has a valid subscription to the service of receiving the CLI; and - control means (28), controlling the transmission of the CLI to the called terminal

(2) in dependence of the check for a valid subscription of the called terminal (2).

7. An equipment according to claim 6, characterized in that the control means (28) is adapted to break the speech path through the second local exchange during a predetermined time adapted to the CLI transfer operation if the called subscriber is not authorized to receive CLI.

8. An equipment according to claim 7, characterized in that the control means (28) is adapted to break the speech path through the second local exchange (22) in both directions during the predetermined time adapted to the CLI transfer operation.

9. An equipment according to claim 7, characterized in that the control means (28) is adapted to break the speech path through the second local exchange (22) in the direction towards the calling subscriber terminal (1) during the predetermined time adapted to the CLI transfer operation.

10. An equipment according to claim 7, characterized in that the control means (28) is adapted to break the speech path through the second local exchange (22) in the direction towards the called subscriber terminal (2) during the predetermined time adapted to the CLI transfer operation.

11. An equipment according to any one ofthe preceding claims, characterized in further comprising remote control means (33, 34) adapted to provide remote control ofthe equipment.