CA1182229A

CA1182229A - Remote meter reader and method for reading meters over non-dedicated telephone lines

Info

Publication number: CA1182229A
Application number: CA000402979A
Authority: CA
Inventors: Alan E. Willis; John R. Lowdenslager; Neal Goldstein
Original assignee: Neptune Water Meter Co
Current assignee: Sangamo Electric Co
Priority date: 1981-05-18
Filing date: 1982-05-14
Publication date: 1985-02-05
Also published as: GB2099260B; US4394540A; GB2099260A

Abstract

ABSTRACT OF THE DISCLOSURE

A meter reader is disclosed for automatically reading utility meters at a telephone subscriber station and transmitting the meter data read to a central office over non-dedicated telephone lines in response to a call initiated by the central office. The meter reader is located at the subscriber station and includes a microprocessor, a telephone isolating device, a call answering device, a ring detector, an off-hook detector, a ring generator, a data transmitter-receiver device and a modem. Each day the telephone is isolated from the telephone lines for a pre-determined data access time. Any call made to the subscriber station during the data access time is answered by the meter reader. A coded signal is sent out over the telephone lines by the meter reader for the purpose of determining the source of the call. If the call is from the central office a coded reply signal is sent back, the meter reader transmits the data to the central office. If the coded reply signal is not returned, the meter reader generates ringing signals for activating the bell in the subscriber's telephone. If the subscriber telephone is picked up at any time during the data access time, it is immediately unisolated from the telephone line.

Description

2~

BACKG~O~N~ ~ Tlll INVENTI()N
,, The prcsent invention relatcs ~enerally to remote readiny of meters and more particularly to a dcvice and mcthod for automatically reading meters at subscriber telephone stations from a remote location, such as a central office over non-dedica~ed tPlephone line~ in response to a call initiated by lthe central office.
~ver the last several years a number of different systems have been proposed for au~omatically readinE utility and other types of meters from a remote location for the purpose of lG eli~ina~ing the high labor costs involved in door-~o-door mPter reading and for providin~. more up-to-date information. Un-for~unately, for one reason or ~nother~ none of these systems have come into wide spread use.
~lany of ~hese proposed systems have iTIvolved usin~
1~ existing, non-dedicated, telephone lines as the co~nunications medium for trans~erring the meter information and have involved obtaining the information in response to a telephone call initiated by the collecting station. The main advantage of using non-dedicated telephon~ lines is that it does not require 2~ installing additional communic~tions lines. The main advar.~ages of transferring the informatil)n pursuant to a call made by the ' collecting station are that it does not re4uire complex answerin~
equipment at ~he collecting station to insure ~hat all incoming calls will be answered in an orderly and efficient manner and 2~ does not involve the use of selectivcly o?erable automatic dialin~ devices a~ each one of the locations containLng utility meters wh.ch are to be read. One of the problcmc wi~h s~ch 2~2~
,;
I systems, however, has been the unavoldat~le rin~,in~ of the telephone at the subscriber station pursuant to the call initiated by the collectin~ office. In order to avoid this nuisance to the subscriber, a numbcr of different techniques S have been sugges~ed.
One such technique involves usin~ s~ecial telephone con~pany line test circuits which will not activatP the bell in the t~lephone at the subscriber s~ation for connec~in~, the collec~ing station wi~h the subscriber station. One of the problems with this technique is that it requires ins~alling ~ ad~itional equip~ent at the telephone company exchan~,e. Also, the technique requires telephone company approval. An example of a system employing this technique is describe~ in U.S.
Reissue Paeent Wo. 26,331 reiss~ed on January 9, 1968,to 1~ Bro~hman et al on original U.S. Paten~ ~o. 3,1ls2,726 dated July 28, 1964.
Another ~echnique involves the use of a ring ~utin~
circuit at the ~elephone subscriber station for muting a portion of the first ring and the use of sequential ringing signals having a different spacing from normal rin~ing signals f~r the call from the collecting office. One o the problems with ~his technique is that it involves complicated cireuitry at ~h~ cen~ral office, and some modification of the eircuitry at the telephone exchan~,e and at the subscriber station.
Another problem with this .echnique is that a por~ion of ~he first rin~ on every incoming call is muted, which is ra.her objectionable. ~n exa~ple of this technique is disclosed in U.S. Pate~t ~o. 4,1269762 lssued on Novemb~r 21, 1978, to ~lar~in et al.

%22 I
!~ Sti!l another tcchniq~c involves ~isconnectin~ the ` subscriber's telephone from the telephone lines for a certain cime period each day and then eonnecting the tel~phone wires ' directly to a meter rca~ing devic~ connecte~ to the utility 5 meters during that time pcriod. The meter rea~in~, device responds to an incoming call by transmitting out the meter dataO One problem with this arrangem~nt is ~hat normal telephone service is completely disrupted for that period.
~ hnother problem with ~his arrangemcnt is that all incoming calls made duriny,tha~ time period, including calls made by parties other than the collectin~ station, will be connected to an~ answered by the meter reading device. Once answered, the meter data will be sent out ovcr the telephone lines, even though the caller may not ~e the collectin~. station. An example of this arran~ement is also disclosed in the above noted U.S. Pate~lt ~o. 4,126,762 A further techni~ue involves the use of switch controlled delaying apparatus a~ the subscriber sta~ion arran~ed so that when a call is received at the subscriber station it is 2~ not connected to the tDlephone until a sufficient amount of time has elapsed to penni~ call ans~ering apparatus at the subscriber station to receive a specially coded signal sent between the first ringing si~nal and the second rin~;in~
signal indicating that the call is from the collecting s~ation.
One of the objectionable aspects of this ~echnique is that the first ringing si~nal is suppressed. An example of this arrangement is dPs~ribed in British Patent No. 905,411 published Sep~ember 5, 1962, to Kienast.

I ~822~2~

., Other known prior ar~ inclu~es U.S. Patent 3,049,59~;
U.S. Patent 3,231,670; U.S. Patcnt 3,266,018; U.S. Patent

3,362,971; U.S. Paten~ 3,376,389; U.S. Patent 3,508,243;
' U.S. Patent 3,551,597; U.S. Patent 3,558,357; U.S. Patent '~ 3,564,143; U.S. Patent 3,742,142; U.S. Patent 3,842,206;
U.S. Pa~ent 3,~68,640; U.S. Pa~ent 3,899,639; U.S.. Patent 3~902,016; U.S. Patent 3,922,4g2; U.S. Patent 3,936,617;
U.S. P~tent 3,937,8g0; U.S. Pa~ent 4,002,837; U.S. Patent ' 4,004,097; U.S. Patent 4,022,927; U.S. Patent 4,059,727;
U.S. Patent 4,086,434; U.S. Patent 4,126,472; U.S. Patent

4,151,371; ~.S. Patent 4, 169,290; U.S. Patent 4,180,709;
U.S. Patent 4,241,237; Bell Laboratories Record, Volume 48 No. 4 (1970) pp. 104-109; the ~merican City and County (Dec. 1575) pp..4?-48i and I~M Téchnical Disclosure Bull-etin, ~eb. 1971), ~-ol. 13, No.9. pp. 2682-2683.

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~ ~A~Y ~F T~iE INVENTION
. . _ I~ is an object of this invention to provide a method for automatically reading meters at a telephone subscriber staeion and transmit~in~ the meter rcadout information to a central office over non-dedicated telephone lines in response to a call initiated by the central office.
,' It is another object of this invention to provide a meter reader for use in automatically readin~, on demand, utility meters at a telephone subscriber station and transmittin~
the meter da~a read to a computer at a central office over non-dedicated telephone lines in response to a call initiatecl by the central office.
It is still another object of this invention to provide a method and meter reader as described above wherein t'ne call initiated by ~he central offiee will not cause the telephone at the telephone subscriber station to ring and which will not substantially interfere with normal usa~e of the subscriber telephone.
It is yet still another object of the invention to provide a method and meter reader as described above with can be used 2~ with existing commercial equipment without modification to the telephone lines or the telephone exchan~e equipment.
It is another object of this inven~ion to provide a method and meter reader as described above that does not interfere with customary meter operations, that is easy to install and ~hat is aecurate in ob~ainin~ and transmit~in~
meter data.

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It ls st L l a l ~ O ~ h~ cbJ~ct C F t ~ c~tion tc p r o v a novel tcchnique for cstablishing telephone communications between a computer at a central office and a computer at a telephone subscriber station over non-dedicat~d telephone S lines on a call initiated by ~he cen~ral office without causin~
the telephone at the telephone subscriber station to rin~ and without in~erferring wi~h normal telephone usage of the telephone at the telephone subscriber station.
A method or reading meters at a telephonc subscriber station from a central office over non-dedicated ~elephone lines on a call initiated by the central office without causing the telephone at the su~scriber s~a.ion to ring and without substantially interferring with normal telephone service at ~he telephone subscriber station acçordin~ to the present invention compxises providing at said subscriber station a selectively operable meter reader which is coupled in series between said telephone lines and said subscriber telephone, which is connected ~o said meters and which is capable of answering telephone calls, isolatlng said subscriber telephone from said telephone lines for a predetermined data access time, initiating a call from said cen~ral office to said subscriber st~tion when a meter reading is desired, but only durin~, said data access time, ans~ering the call with said meter reader, conEirming that the call received is the call initiated by the central office, and not from another party, and transmi~ting said meter data to said central officc if it is confirmed that said call is from said central ~ffice.

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~ 32Z~9 I A me~er ~eader or re~ding meters et a ~elenhone su~s~iher i station fron~ a central office over non-dedicated telephone lines on a call initiated by the ccntral office without ' causing the telephone at the subscriber station to ring and without substantially interferrin~ with normal telephone service at the telepnone subscribcr station accordin~ to the present invention ~comprises means for selecti~ely isolatin~
said subscriber telephor.e from said telephone lines for a ' predetermined da~a access time, mcans for detecting a ring generating signal to said subscri~er station during said data acce~s t,m~ indicating an incoming call, means for answerinc said call causing thereby said rir,ging signal to termina~e, means for ascertaining if 6aid call i~ from said central office, and means for collecting,meter da~a from said meters and trans~itting said meter data to said central o~fice if said call is from said central o~fice.

, ., ~

~8222~

~Rl~r D~SC~Ii'lIG;i ~ liir, U~
!
In thc drawings whcrein like re~ercnce numerals reprcsent like parts:
Fi~ure 1 is a block diagram of a system for remotely reading utility meters incorporatin~ the meter rcader of the present inven~ioni Figure 2 is a flow chart showing ~h~ operation o the system in Figure li and Figure 3 parts ~a), (b), (c) and (d) is a detailed schematic diagram of another embodimcnt of the mcter reader shown in Figure 1.

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'' DETAILEL) DESCRIPTION Ol_P~ K~.~D ~rl~ lE~l~
. .
The present invention is concerned with a system for automatically collec~ing meter da~a in a computer in a central office from utility meters at telcphone subscriber stations over non-dedicated telephone lines on a call initlated by the central office.
The syste~ is cen~red around a microprocessor controlled meter reader which is located at each subscriber station. The meter reader is coupled to the utility me~ers whose contents are to be read, to the telephone lines and to the telephone at the subscriber station.
The me~hod for carrying out the system involves isolating th~ telephone at the subscriber station for a predetermined data access ~ime each day, answering all incoming calls during the data access time with the meter reader and arran~ing to I have the central office call the subscriber station for meter readings periodically but only during the data access time.
If a call received durin~, the data access time is determined by ~he meter reader to be from the central office, data signals corresponding to the current meter readin&s are collected I from the meters and are sent out to the central office over the telephone lines. If a call received during the data access time is determined by the meter reader not to be from the cen~ral office, the telephone is caused ~o ring through rin~ing signals generated by thc meter reader. At the same ~ime, simulated side ~one signals are 2enerated by ~he meter reader and sent out over ~he telcphone lincs so tha~ the caller will actually hcar si~nals sounding like thc ringing of the subscriber's telephone. If the telephone is picked up during . ;

the ~t~ ~_cess ~i.,.2, c~th.r ~c ~ r. ou go-ng ~1L or ii.
response to the ringing of the telcphonc bell causcd by ringing signals sen~ out by ~he me~er reader, the off-hook condition is sensed by the meter reader and the telephone is unisola~ed from the telephone lines. The technique for de~ermining if an incoming call duri.ng the data access time is from the central office involves sending a coded signal I.out over the telephon~ lines. Xf the incoming call is rom the ! central office, a coded acknowled~ement signal is promptly . returned.
At all times other ~han ~he da~a access time, the telephonè is unisolated from the ~elephone lines and is used . in the normal manner.
As can be appreciated, tha system completely avoids l~ringing of the subscriber telephone on the call from the central office, but will cause the subscriber telephone to ring in response to all other incomin~, call either outside of the data access time or during the data access eime.
~ Referring now to the dr~wings there is illustrated in Figure l a block diagram of an embodiment of an overall system j for remotely reading utility meters at telephone subscriber t stations over non-dedicated telephone lines according to the present invention and identified generally by reference numeral 11.
I System ll includes a eentral office 13 for collecting meter da~a which is connec~ed to a telephone company telephone exchange 15 through telephone lines 17. A plurality of telephone subscriber stations l9-l, 19 2 and 19-3 etc. are also connec~ed to ~elephone exchange 15 through telephone lines 17, the nu~.ber of subscriber stations sho~n being for illustrative purposes only.

!~ Central offise ] 3 includes a comPuter 21 equippcd with . a sui~able telephone dialing mechnaism 23. Computer 21 is coupled ~o telepnone lincs 17 ~hrough a modcm 25 which serves I to convert output si~nals from conlputer 21 to a form suitable I Eor ~ransmiss;on over telephone lines 17 and to convert incomin~
signals from telephone lines 17 to a form compatable with : computer 21.
Each one of the subscriber s~ations 19 ~ncludes a ~ plurali~y of utility meters such as a gas meter 27-1, an , electric meter 27-2 and a water meter 27-3, each of whose ' contents it is desired to read. Utility meters 27 are 1 conventional type utility meters which display the amount of the product consumed with a series of dials. Each utility I meter 27 is coupled to a pulse~enerating device labelled 29-1, 29-2 and 29-3 respectively> which converts the dial . readin~s of its meter into pulses. Each pulse generating . .
!, device ~9 is coupled ta a counter/memory device labelled 31-1, 31-2 and 31-3 respectively, ~hich counts the number of pulses received from its associated pulse genera~ing device and stores t~e count in ~igital form. Pulse generating devîces and counter/memories for ~his purpose are well known in the art and disclosed, for example~ in U.S. Patent 3,937,890. If utility meters 27 are digital type meters which include readable memories for storin~ the meter readings directly in digital form, the pulse ~enerating devices 29 and coun~er/memories 31 are omitted. Each subscriber s~ation 19 also includes one or more convcntional telephones shown in Figure 1 as a single telepnone 33 which is equippcd wi~h a ringing device sueh as a bell (not shown).

ol2-z~

¦l ~ach subscriber ~ation l9 iurLhe~ c1u~les ~ metel reader 35 constructed according to the teachings of the prescnt invention for controllin~ the transmi.ssion of ~eter data fro~
counter/memories 31 to the computer 21 at central office 13

5 and for selectively con~rolling the operations o telephone 33.
Meter reader 35 is couple~ to each onc of the counter/~.ci,lories 31 through a separate 8 bit bus labelled 37-1, 37-2 and 37-3 respectively. PIeter reader 35 is also connec~ed electrically in series between a pair of ~elephone lines 17 and a pair of subscriber station lines 39 which are connected to telephone , 33 and preferably is connected at a place between a lightning ~ arres~or 41 which may be a~ subscri~er station 19 and telephone 'i 3~. Meter reader 35 is physically located at any convenient , area on the premises of subscrfiber station 19.
Meter reader 35 is organized and built around a micro-processor 43 which provides the necessary con~rol and sequencing for the operation of the device and includes the necessary arithmetic and logical functional blocks for operating the device and handling the flow of data from meters 27 to central office 13. In addition to microprocessor 43, meter re~der 35 includes a telephone isolating devcie 45, a ring detector `47, a call answer device 49, a ring generator 53, an off-hook detec~or 55, a UART 57 and a modem 59.
Telephone isolating device 45 is in the form of a relay having a pair of nonmally slosed switches 45-1 and a coil 45-2.
. Relay swi~ches 45-1 are coupled in series between telephone lines 17 and telephone subscriber lines 39 and connec~ed to :coil 45-2. Relay switches 45-1 serve either to isolate telephone lines 17 from telephone 33 or to "unisolate" that 2~ ~ ~

is, rcconnect telephone lines 17 to telephone 33 on signals receivcd from microprocessor 43 over line 61. During the time period outside th~ ~ata access ~imc, rcl~y switches 45-1 are closed and telephone 33 is connec~ed to lines 17 and is used in the normal manner. During thc data access ~ime, relay switches 45-l are opened, isolating telephone 33'from ~elephone~
lines 17 and remain open unless closed again to unisolate the subscriber telephone 33 on instructions from ~icroprocessor 43. Ring detector 47 ig connected across lines 17 and functions lQ to detect ringing signals over lines 17 which are generated by central office 13 to indicate an incoming call and then send a logical signal indicating this condition to microproc~ssor l 43 over line 63.
,; Call-answering device 49,answers all incoming calls ~ when relay switches ~S-l are open and includes a relay having a normally open switch 49-l, a coil 49-2 and a resistor . ~9~3, having a resistance equivalent to that giving an of-hook condition which at the present time with most telephone companies is typically 600 ohms. Relay s~itch 49-l is coupled across lines 17 in series with resistor 49-3 and is connected to relay coil 49-2. When a ringing signal is detected by ring generator 47 durin~ the data access time a signal is sent by , microprocessor 43 to relay coil 49-2 over line 65 closing relay switch 49-l. This causes an impedance drop across lines 17 in a manneF identical to the impedance drop when telephone 33 is picked up (removed fro~ its cradle). This impedance drop is detec~ed by the telephone exchange which responds tc ; the impedance drop by turning off its ring si~nal ~enerator.

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¦l Ring genc~ator 53 is coupled across lin~s 17 and across ¦' lines 39 and generaLes a 90 vol~ R~IS ~0 HZ signal (similar - I to the ri.nging si~nal~ sent over lincs 17 by telephone exchan~e ¦, 15) and a 3/4 volt RMS 20 HZ signal ~similiar to the ringing signals heard by a caller when the telephone is ~inging at the station called) when instructed to do 50 on a signal from ' microprocessor 43 over line 67. The ~0 volt ~MS 20 HZ
signal is sent over lines 69 ~o telephone 33 over line 39 and ~ causes the bell in telephone 33 to ring. The 3/4 volt R~IS
, 20 HZ signal is sent out on lines 17 over lines 71 and serves to simulate ringing or sidetone signals to the caller.
Off-hook detector 55 is coupled to lines 39 over lines !~ 56 and serves to detect when telephone 33 is picked up from ~ its cradle, (i.e~) that is~ placed in an off-hook condition), ' at anytir.le and transmit a status signal of this oondition to microprocessor 43 over line 72.
UART 57 takes 8 bit parallel data received from micro-processor 43 over an 8 bit bidirectional bus 73, converts ~he , data into serial rorm on a ~ignal received from microprocessor 43 over line 75 and ehen sends the data to modem 59 over line 77. VART 57 also takes serial data received from modem 59 over line 77, converts it in~o parallel form and senas it back to microprocessor 43 over bus 73 on signals received from microprocessor 43 over line 79. Modem 59 takes serial data from UART 57, converts the data in~o signals suitable for transmission over telephone lines 17 and transmi~s the si~nals to line 17 over lines 81. Modem 59 also recei~es signals sent over line Bl frvm lines 17, converts the signals into a ~ 18~:Z29 ornl suiLaDie ~or pro~L~s~ing by l"icroproccssor 43 an~ then sen~
~he signals ~o ll-~RT 57 over line 77. From UART 57 these latt~r s g~als are sent to microproc~ssor ~3 over bus 73.
Modem 59 also sends its carrier si~nals over lines 17 through lines 81 on signals received from micro~rocessor 43 ' over line 83 und sends a signal to microprocessor 43 indicating ,. carrier signals received from modem 25 at central office 13 over lines 81 from lines 17 to microprocessor 43 over line , 85. hode~ 59 is compa~able with mo~cm 25 at central office l, 13. For example, modem 25 may be an "originate~' modem having carrier frequencies of 2025 and 2225 HZ and modem 59 may '. be an "answer" ~odem having carrier ~requencies of 1070 ,~ and 1270 HZ.
I~ Meter reader 35 also incl~des ~ power supply ~no~ shown) 15 for supplying the necessary operating power to the various ; components requiring power.
- The microprocessor 43 i5 programmed to keep the time of day through means known in.the art by counting time intervals ' generated by its internal clock and using these to incremen~ :
: the ti~.e of day information stored either in registers or random access memory locations.
In the operation of system 11, meter reader 35 is controlled in response to the time of day clock programmed into microprocessor 43 to isolate a telephone 33 from telephone ' lines 17 for a predetermined data access time each day.
Computer 21 is programmed to initia~c a call to subscriber s~ation 19 periodically for the purpose of obtaining meter readings, bu~ only durin~ the data access time. The da~a access time is preferably chosen for a time which is least li~ely to inconvenience ~he subscriber, such as from 2:G0 A.~l.
to 3:00 A.~

.

~ 2 ~
! Accordin~ly, metcr readcr 35 first determines throu~h ,~ microprocessor 43 if a data access time exists. If the data access ~ime does exist, microprocessor 43 checks through off-~ hook detector 55 to see if telephone 33 is being used by the subscriber. If the telephone 33 is being used, microprocessor ~3 simply ~aits until such use has terminated. If the telephone 33 is not being used, microprocessor 43 opens relay switch 45-1, which is normally elosed, isolatin~ telephone 33 from i telephone lines 17.
10 1 If telephone 33 is picked up by the subscriber at any time during the data access time to make an outgoing call, the conditon is immediately dctected by off-hook detector 55 and relay switch 45-1 is closed so ~hat the telephone 33 may be used by ~he subscriber. After the telephone has been used, relay 45-1 is re~opened if the time is still within the da~a access time.
Any incoming call made during the data access time, including a call which may be made by central office 13, is , detected by ring de~ector 47 and immediately answered by 20 answer call device 49. As soon as the call is answered, the ' ringing signals from the telephone exchange 15 are terminated.
; Since telephone 33 is isolated from telephone lines 17, the ringing signal generated from telephone exchange 15 indicating the incoming call is being made is not detected by telephone 33 and the bell in telephone 33 is not activated.
After a delay of about one second, meter reader 35 sends a co~firmation signal out ovcr lines 17. If the call answered is from central office 13 an acknowlcdgem~nt signal is re~urned within abou~ one ccond. The confirmation and acknowledgemcnt signals ar~ genera~ed by th.e modems at each 2~
I`
ocati~n. S?c^ fica~ the con~rm~ion si~ ener~
1 by causing modem 59 to turn on its transmission carrier and ,~ send its carrier out over lines 17, with the carrier constituting ~! the confi~mation signal. If the incoming call is from central office 13, the carrier signal of modem 59 is detected by computer 21, which turns on its modem 25 and sends i~s trans-1, mission carrier out over lines 17, with ~he carrier from 1~ modem 25 cons~i~utin~ ~he acknowledgement signal. The I total time interval during which the confirmation signal is '' sent and the acknowledgement signal is received is about one second.
If an ac~nowledgment signal is received by meter reader . 35, microprocessor 43 concludes that the call is from ~he ~ cen~ral offic~ 13, collec~s the meter readings from counter me~ories 31, eonverts the 8 bit parallel meter data in~o ,. serial data in UART 57, and sends the data through modem 59 ..' to central office 13 over lines 17 along with identifica~ion ' data of the particular location of subscriber station 19 I~ which is stored in a memory in microprocessor 43.
: If the acknowledgment signal is not returned, microprocess 43 interprets this to mean that the call is not from central office 13. In this situation, microprocessor 43 promptly actuates ring generator 53 causing it ~o send ~ut its ~70 signals, one through lines 59 to lines 39 for activat-ing the bell in telepho~e 33 and the other through lines 70 ar.d lines . 17 or simulating ringing side tones over lines 17 sg that the c~ller will hear a ringing sound a~ his end. Ring gener~or 53 is needed to send ringing signals to ~he bell in telephone 33 since~ as far as the telephone exchange 15 is concerned the call has already been answered. As is kllown, once a call -~8~;~2~
I. hd~ ~eel-~ answeLeu, the rin~ ~ign~' g~,.c-atlr~g r,~c~ait~y -t the telephone exchan~e is not desi~,ned ~o be r~activated.
; Furthermore, even il- the eircuitry cr~uld be reactivated, the signals would not reach telephone 33, since telephone 33 is isolated from telephone lines 17. Bo~h signa1s generated ; by ring generator 53, are sen~ ou~ over their respective lines j for a suffieient time interval to enable the su~scriber to : answer the telephone, such as sixty seconds. I the telephone 33 is no~ answered wi~hin that time the rin~ing and side-tone signals are terminated. The signals are also terminated if telephone 33 is picked as a result of the ringing signals.
If telephone is picked up turing the data access time either in response to ringing signals generated by ring i ~enerator 53 or for the purpose~of makin~ an ou~going ca~l, a signal indicating the off-hook condition is sent by off-hook ~: detector 55 to ~icroprocessor ~3 and microprocessor 43 responds ~o this signal by sending a signal over lines 61 to close . relay 45-1 and thereby u~isolate telephone 33 from telephone ,: line 17.
As can be appreciated, if a call is made to a subscriber 1 station 19 during the data access time by a party other than central office 13, there will be a very small delay period of about two seconds before telephone 33 is eaused to ring through I ringing signals generated by ring generator 55 and simulated side tones are g~nerated by ring generator 53. During that delay period the caller will only hear a short "beep"
' ' I' corresponding ~o the outgoing confirmation signal rrom mo~nl ~9.
¦ If a call is made by another party durin~ the da~a access time and at a time when meter reader 35 is in communication with 1 central orfice, line 17 will be busy and indicated as such to , the caller.
If the sub~criber picks up telephone 33 during ~he data aceess time and while the meter reader 19 is in communication with the central office 13, ~he ~ransfer of da~a from meter , reader 19 to central office 13 is aborted.
' At the end of the data access time, relay switch 45-1 ~; is closed. Meter reader 35 is ef~ectively dormant during the time outside the data access time interval and remains , dormant until the start of the data access time the next day.
The operation o the syst~m is shown in detail in the , fio~ chart in Figure 2.
Referring now to Figure 3, there is illustrated a detalled schematic diagram of another embod,ment of a mPte~ reader - constructed according to the teachin~s o the present in~ention ' and identified by reference numeral 135. Me~er reader 135 ' performs the same functions and operates in substantially the same manner as meter ~eader 35 shown in block diagram , form in ~igure 1. T~l~ main differences in meter reader 135 are that (l) the ring detector circuit is also used to detect an off-hook condition during the time period outside the data access time, ~2) a separate off-hook detector is included for detecting an off-hook condition in the ~ata access time period, (3) the UART is omi~ted and the UART fun~tions are performed instead by the microprocessor, and (4) separate .. e~

8z~29 components are include~ oi ~enela.i..g the tlmc cf ~a; .for- ;
mation si~nals and storing the address of the subscriber ;station. In addition, meter reader 135 is shown applie~ to a ' three wire telephone system 117 rather than a two wire ~elephone , system as in Figure 1.
Meter reader 135 includes a m;crsprDcessOr U8~ a telephone , isolating circuit 145t a combination off-hook an~ data access time ring detector circuit 147, a call answer circuit 149, a l non-data access time rin~ generator cirucit 153, an off-hook detector circuit i55, a modem assembly 159, an address store 161, a clock 163, a power supply 165 and other associated interconnecting components.
Microprocessor U8 may be, ~s an example, a National Semiconductor COP420L 5ingle Ch~p ~-Channel Microcontroller and is connected to a 2 MHZ crystal XTALl which is coupled in ' parallel with a resistor R47. ~licroprocessor U8 performs all the functions performed by microprocessor 43 except for storing the address of the subscriber.station and providing the time of day check signals for the data access ~ime and in addition performs all the functions provided for in UART 57. Micro-processor U8 receives time of day olock signals from clock 163, which ~re sent over line 191 to line 193 and then from line 193 to line 195, subscriber address signals from address store 161 which are sent over line 193 to line 195 and meter data signals which are sent from the meter interface uver line 195.
; Microprocessor U8 also receives status signals from off-hook and rin~ detector 147 over line 197, from off-hook detcctor 155 over line 199 through a type D model 4013 flip-flop U7 and Z 2 2 ~
data signl~ls from modem assembly 159 over line ~01 througn a 2N4401 transistor Q5 which is connect~ in series with a ~ resistor R51. Microprocessor U8 also receivcs a signal ,~ indicating the presence of a carrier signal from the mode~
S at the computer at ~he central office acknowl2dgin~, that an incoming call is from the central office over line 203.
Telephone isolating circuit 145 in Figure 3(a) performs , the same function as eelephone isolating device 45, of i Figure 1, namely, to isola~e or unisolate the telephone set a~ the subscriber station from the outside t~lephone lines 117 on signals received from microprocessor U8 over line 205 through a resistor R5. Telephone isolating circuit 145 I includes a relay ~ing a coil 145-1 and a plurality of relay , switches 145-2, 145-3, 145-4 and 1~5-5 and an MPS14 transistor .; Q3, which functions as a relay driv~r. When the signal on line 205 is low, relay switches 145-2 through 145-5 are in the position as shown in Figure 3 and lines 139 connected directly to the telephone se~ are connected to ~i.e..unisolated ' from) telephone lines 117. On the o~her hand, when the signal over line 205 is high, transistor Q3 conducts and relay switches 145-2 to 145~5 are moved ~o the posi~ion opposite . that shot~ in Figure 3 and the telephone see lines 139 are isolated rom telephone lines 117.
Off-hook and ring dete~tor 147 is used to detect (1) ~5 an off-hook condition at any time in the time period other than during the data access time and S2) a rin~ing signal indicating an inco~ing call sent over the telephone lines 117 by the ~elephone e~cllange during the time period during ~he d~ta access time. Detector 147 includes a bridge rectif~er I CilCUit 147-~ having ~o-~r T~914 diodcs CRl, C~ , CP~3 ~nd C~
¦ a model number MCTl line isolator Ul which includes a ligh~
emitting diode and a pho~transistorand a spike filter I, circuit comprising a resistor R1, and a capacitor C5 for l' eliminating noise. The outpu~ signal from off~hook and ring ~I detector 147 is sent to microprocessor 147 over line 197.
Ii When a ringing signal is sent in from lines 117, it passes I through the bridge rectîfier circuit 147~ hrough the light emi~ting diode in the isolator Ul where it is sensed by l, the phototransistor and then sen~ back through the brid~e rectifier circuit 147-1 to switches 14S. If switches 145 are in the unisolated position, the signals are sen~ to the telephone set of subscriber~ If switches 145 are in the ~ isolated positon, the signals ~re not sent ~o the telephone ~ set of the subscriber. When the telepho~e set is picked up at a ~ime o~her than during the data access time, the volta~e 1. appearing across the line causes a small current to flow j through the brid~e rectifier.circuit, through the diode ,! -I in line isolator Ul where it is detected by the phototransistor ': in line isolator Ul and then back through the bridge rectifier circuit 147-1 to telephone ~ines 117. The purpose of detecting an off-hook condition outside o the data access time is to prevent disconnecting a subscriber who is using the telephone at the start of the data access time.
Call answer circuiL 149 is functionally similar to call answer circuit 49 to Figure 1 and includes a relay having a . coil 149-1 and a switch 149-2, a 620 ohm resistor R3 and an ~SA14 transistor Q4. Switch 149-2 is coupled across tne ring and tip lines of telephone lines 117 in series wich ~he 600 ohm resistor R3. Transistor Q4 is used as the driver for 2;~
1. , j' ~he lelay. ~en rel2y s~itch 14~-3 is closcd, the 620 oh resistor R3 is couplPd across the tclephone lines 117 ' causing the telephone exchange ~o terminate the ineo~ing , ringing signal. The si~nal to close relay switch 149-1 is sent to transistor Q4 by microprocessor U8 over~line 207.
,j Ring generator circuit 153 genera~es a 90 volt 20 ,I cycle signal for ~ctivatin~ the bell in ~he subscriber telephone set and in addition a 440 H2 sine wave si~n~l which is sent out over telephone lines 117 simulating side-tone signals that . would be heard by a ealler if the bell in the subscriber set were ringing. Both si~nals are generated on ins~ructions from ; microprocessor U8 if an incoming call is made during the data ; access tl~e . and it is determined that the call is not from the central office. Ring generator circuit 153 includes an oscillator circuit 153-1, a vcltage mul~iplier circuit 153-2, an MCT2 ~ype isolator U2 and connccting circuitry including . , resistors R9 through R20 and R43, two IN914 diodes CR16 and CR18, two 2N4401 transistors Ql and Q2 capacitor C10 a ~LM324 op-amp U5-3, a ~L~i324 op-amp US-2 and a ~LM32V op-amp U5-4.
Oscillator eir_uit 153-1 includes an ~LM324 o?-amp U5-1 and a filter circuit ~rranged in negative feedback and including resistors R44, R4s and R46 and capacitors C21~ C2~ and C23.
Voltage multiplier circuit 153-2 includes capacitors C7 and C8 and two IN4004 diodes CR14 and CR15. The 20 cycle signal ~5 and the 44n~z signals are ~enerated from a 120 vol~ 60 HZ
signal received from the ex.ernal power source over lines ?09 . and a 20 H~ signal received from nlicroproc~ssor U8 over line 211.

!i ~22~2~
~ 2011% si~,r~ s ,e~t ~i.i~ll~J throu~h. '1~~rS U5-~ ~nd '~ U5-3. From op-amp U5-3 one portion, which is used ~o ,P,enerate i' the 440 HZ side tone si~nal, is fed into the positive input ~ of a ~L~1324 op-amp in oscillator circuit 153-1. The output 1 si~,nal from oscillator circuit l53-l is fed into ~he postive inpu~ of op-amp U5 4 whose output is connec~ed ~o modem ass,embly 159. The other por~ion of ~he si~,nal output si~naL
of op amp U5-3, which is used ~o ~enerate the 20 cycle ringing signal, is sent to transistor Q2, from transistor Q2 to 10 1 isolator U3 and from isolator U3 ~o ~ransistor Ql and voltage multiplier circuit 153-2 and from there to the tip and ring lines of the telephone subscriber set over lines 213.
Off-hook detector circuit 155 includes an ~ICT2 isolator U2 identical to isolato~ Ul in pff-hook and ring detector 149 , and associated co~;~pone~try-including a ~Fe~is-t~r R6, an 1~914 diode CR9, resi.stors R7 and R8 and capacitor C6. Off~hook . detector circuit 155, func~ion5 to detect an off hook ; condition in the telephone at the sub.scriber station during , the datà ~ccess time^a~d sen~s a si~,nal-indieating this condition to microprocessor U8 over line l99 throu~h ~lip-flop U7. A
separate o~f-hook detector is needed for operation durin~, the ~ta access ti~e s.ince there i~ no current flowing through the telephone set lines 139 when ~he telephone se~ is isolated : and hence no current chan~e when ~he telephone set is plac~d from an on hook to an off-hook condition. Off-hook de~ec~or circuit l55 applies a small voltage ~cross telephone set lines 139 during the data access ti~e so ~hat when the telephone set is placed in an orf-hook condition a small curren.
~ change will occur,. and operate the tclephone isola~ing circuic 145 through m.icro~rocessor U8.

>5_ ~

~lodem asse~bly 15Y performs cile same Luncciorl~ a~ Illod~
59 and includes a modcm U9, a divide-by-two flip-Elop U7, a sumDing amplifier circui~ 159~ duplexer circuit 159-2, a limiter circuit 159-3, an isolation transormer T2, a band-S pass filter 159-4 and two level dctector circuits 159-5 and 159-6. ~lodem U9 may be a Motorola Universal l.ow Speed ! Modem model ~umber MC14412 having transmit~er carrier frequencies of 20~5 and 2225 ~Z.
, Summing amplifier circuit 159-1 includes a ~LM324 op-amp ~ U6-1 resistors R39, R40 and R41 and capacitors C19 and C20.
Duplexer circuit 159-2, which is coupled to the output of op-amp U6-1, includes a ~LM324 op-amp U4-1 and resistors R29, , R30, K31, R32 and R33. Limiter circuit 159~3l which is coupled ' ~o the positive input of op-amp U4-l, includes two IN414 diodes CR12 and CR13. ~and pass ilter circuit 159-4 which is coupled to the output of op-amp ~4-1 includes three ~L~i324 op-amps ' U4-2, U4-3 and U4-4, resistors R22 throu~h ~29 and R4g and . capacitors Cll throu~h C16. .Band pass filter circuit 159-4 has . a pass band of 1070-12?0 HZ, which is equal to the upper and lower transmitting carrier frequencies of the modem at the .. central ofice. Level detector circuit 159-5 is coupled to the output of band-pass filter circuit 159~4 and includes a ~L~1324 op-amp U6-2 and a pair o~ resistors R50 and R54.
~ Level detector circuit 159-6 is also coupled to the ou~put of band-pass filter circuit 159 4 and includes a ~LM32~ op-amp U6-3 ~nd a pair of resis~ors ~37 and R38. The output of lev~l detector 159-5 is connected to microprocessor U& ~hrough line 2 ~ .

I~ 229 and tne out~ut or levci detecLor circuit 159-6 is conneccea to the RX carrier terminal of modem U9 through line 23.
' The 440HZ sidetone signal from rin~ generator 153 is fed into the negative input of op-amp U6-1 in summin~ amplifier ~ circuit 1~9-l through resistor R40. The output signal from I op-amp U6-1 is transmitted over linc 215 throup,h limiter circuit 159-3 to the 600 ohm side of transformer T2- ~e resulting si~nal appearing on the goo ohm side of transformer T2 is sent out over the ring and ti.p lines of ~elephone lines 117.
10 , All outgoing data signals are sent from microprocessor U8 to modem U9 and then from modem U9 to the negative input : of op-amp U6-1 in summing arllplifier circuit 159-1 through capacitor C20 and resistor R41. From there, they travel along i the same path as the 440HZ sidetone si~nal. The outgoing I transmitter carrier signals from modem U9 for ascer~aining if an incomîng call is from the central office also travel the -same path.
Incoming data si~nals along with the trans~itter carrier ~, (acknowledgement) signal from the modem in the cen~ral office received over lines 117 are sent to the 300 ohm side of transformer T2. From ~he 90~ ohm side of transformer T2, the ; signals are passed through limiter circuit 159-3 to the ! positive input of op-amp U4-1 in duplexer circuit 15g-2. The output of op-amp U4-1 is passed through band-pass filter 1594 and then split into two parts. One part, ~hich is used to detect the presence of the transmitting carrier from the mode~l at the central office, is sent along line 227 to 1evel detector 159 5. The other part, which is used to send the . incoming data to mode~n U9, is transmiLted over line 225.

~8~
- ii Ad~,css ^tcre 161 inclu~es a n~;r of 4051 type multi-~,plcxcrs U10 and Ull and a series of switchc~ 161-1. Whcn instructed to do so by microprocessor U8, multiplexers U10 ' and Ull sc~ln switches 161-1 con~aining ~he address of the S `` subscriber station and send the data to the microprocessor U8 over line 195.
Clock 163 which supplies timc of day and ~iming signals ~' to microprocessor U8 over lines 191, 193, and 195 includes a ¦. conventional watch chip U14, such as an Intersil 1159H, and o ! a pair of multiplexers U12 and U13. Time of day signals . received by multiplexers U12 and U13 from watch chip U14, are sent ~o microprocessor 143 over.line 191 through lines 193 and 195. - i ~ Of course, the time of day,information signals can also be generated by progra~min~ the microprocessor and adding ` a random access memory ~o store the time of day information ,. for retrieval by a suitable software subroutine added to the ,, microprocessor control program. The subrouting could also ~ include provisions for setting or updating the time of day ,, through signals over the telephone line from the central ofice and also for changing the data access time, The use of a watch chip is simply a convenience in the present ~, embodiment for providing ~ime of day information signals from a conventional and readily available component~
Power supply 165 includcs an IN4001 bridge rec~ifier circuit 165-1 made up of four diodes CR5, CR6, CR7 and CR8, a first regulator circuit made up of an LM341P regulator U15 and two capacitors Cl and C2 and a second regulator circuit made up of an L~1320L regulator and two capacitors C3 and C~.
The output P of first regulacor circuit is +5V and the output M of second regulator circuit is -5V.

-2~-,1 ter reauer 135 opcrates in su~stanLially the same manner as mcter reader 35.
I, Durin~. the time pcriod other ~han the data access ti~e, !I there is no sir~nal over line 205, the switch~s in relay 145 are in ~he position as shown and the subscriber telephone set 1 is oonnected to (unisolated from) the telephone lines 171. If the subscriber telephone is placed in an off hook condition . ~t ehe time when ~he dat~ access ~ime commences, this condition '.
~' is detected by the off-hook and ring detector 149 and a signal ,, indicating this is sent to r.licrcprocessor 143 over line 197.
', A~ the start of the data access time, if the subscriber telephone is n~t in use a signal is sent from microprocessor U8 ' over line 201 to flip-flop U7-2. The Q output from flip-1Op , V7-2 is connected via line 205 to relay Driver Q3 which causes , swi~ches 145 to swi~eh to the position opposite to that shown, isolatin~ thereby the subscriber telephone from the telephone ~l lines 171. If an inc~ming call is made during the data access ' time, the ringing si~nal from the central office is detected , by off-hook and ring detector 147 and a siy?~al to this effect is sent to microprocessor 143 over line 19-l. After a one ' second delay, microprocessor 143 causes modem V9 to send its ' carrier si~nal ~requencies through summin~ amplifier 159-3 to the duplexer circuit 159-4, from the duplexer circuit 159-4 I to the 600 ohm side of isolation transform~r T2 and then from the gao ohm side Qf isolation trans~ormer T2 ou~ over lines 117. If ~hz call is from the central office, the computer there will detect ~he carrier signals and cause its modem to send it transmittin~. carrier signals ovcr the telepho~e lincs 117.

., ~, zz~ l i Th~ ret~lrned civnals witl pa~ss throurh isolation transformers T2, through duplexer circuit 159-4, through ~and-pass fiiter circuit 159-8 which is connected microprocessor U8 within abou~
l two seconds. If the signal is detected, microprocessor U3 ~ will send the meter data out over lincs 117. If ~he incomin~
call is not from the cen~ral office there ~Jill be no return 1 signal. In this case microprocessor will cause ~he telephone ¦ to ring with ringing signals generated in ring Eenerator 153 ¦` and send side ~one si~nals also generated in ring generator 1 153 out ove~ lines 117 through lines 153. Off hook detec~or 155 will sense when the telephone is picked up ~nd cause telephone lines 139 to be unisolated.

.
.

1. . ' .

i. '.
,; ' , '; -30-22~2~
T~pieal ~alucs ~ chms fcr t~ c~.~to~ eter ~~aAc-135 mayb~ as follows:
i'.

Rl - 10~l R21 - 620 R41 - lOOK
I R2 - lM R22 - 8870 R42 - 1~
I R3 - 620 R23 - 2550 R43 - lOM
, R4 - 30K R24 - 237K R44 - 3gK
. ¦~. R5 - 30K R25 - 1240 R45 - 390K
jl R6 - 33 R26 - 21.5K R46 - 3.9M
¦I R7 - lOM R27 165K R47 - lOM
' R8 - 1~ R28 - 845K R48 - 20K
, R9 - 5K R29 - 15K . R49 - 97.6K
R10 - 82K R30 - 12K R50 - lOOK
Rll - 3.3K P~31 - 12~- R51 - lOK
;j .
~I R12 - 75 R32 - 470 R52 - lOOK
, R13 - lK - R33 - 2K R53 - lMEG.
. R14 - 2.4~1 R34 - 150K R54 - 33K
R15 - lOK R35 - 1.5M
I, R16 - loK R36 - ~8 ¦l R17 - lOK R37 - 2K
' R18 - 20K R38 - 2K
R19 - lOK R39 - 820K
R20 - lOK R40 - 200K
,, .

i Typical value in microfarads, unless otherwise stated, . for the capacitors in meter reader 135 may be as follows:

. ......

22~
li 3 Cl ~ 7û/~ C15 - .01 IIC2 - CA 22/16 C16 - .01 ¦ C3 - CA 22QJ35 C17 - .02 ~ C4 - C~ 22/16 C18 - .02 S I C5 - .1 C19 - 180 Picofarads IC6 - .0~ C20 - .01 IC7 ~ 5 C21 - .0~
IC8 - 5 C22 - 2000 Picofarads iC9 - .47 C23 - 200 Picofarads i,C10 - .02 C24 - .02 Cll - .01 C12 - .01 ~13 - .01 IlCl4 - .01 All diodes may be model ~umber lN914.

It is to be understood ~hat although the invention has ' been described sp~ci~ically wi~h reference to utility meters is is obviously also applicabie to and usable with meters monitorin~ consumption of products other than ~as, water and power or olonitoring services~ such as TV usage meters, which may be at a telephone subscriber sta~ion. Also, the data access time may be arranged to occur on a weekly or monthly bases etc., rather t'nan on a daily basis and may be for . intervals greater than or smaller than the one hour interval between 2:00 A.M. and 3:00 A.~. described above.
Although particular embodiments of ~:he inven~ion have been described and illustra~ed herein, it is recocnized that modifications and variations may readily occur to those skilled in the art and consequen~ly, it is intended tha~ ~he clair,ls be ' inte~preted to cover such modifications and equivalen~s.

,. .

Claims

WHAT IS CLAIMED IS:

1. A method of transmitting meter data to a central office from meters at a telephone subscriber station over non-dedicated telephone lines in response to a call initiated by said central office and without actuating the ringing device in the subscriber telephone at the telephone subscriber station, the method comprising:
a. providing at said subscriber stat on a selectively operable meter reader, said meter reader being coupled in series between said telephone line and said subscriber telephone, being connected to said meter, being capable of answering telephone calls and having clock means keeping time of day, b. isolating said subscriber telephone from said telephone lines for a predetermined data access time, c. answering any call received with said meter reader when said subscriber telephone is isolated, d. confirming that the call received is the call inititated by the central office, and e. transmitting meter data to said central office if it is confirmed that said call is from said central office.

2. The method of claim 1 and further including unisolating said subscriber telephone from said telephone lines whenever said subscriber telephone is placed in an off-hook condition.

3. The method of claim 1 and wherein isolating said subscriber telephone for a predetermined data access time is initiated and terminated by said clock means.

4. The method of claim 1 and further including generating signals for activating the ringing device in said subscriber telephone for a defined time interval if said call is not from said central office.

5. The method of claim 4 and further including generating sidetone signals simulating ringing signals and sending said sidetone signals over said telephone lines at the same time as signals are generated for activating the ringing device in said subscriber telephone if the call received by the meter reader during said data access time is determined not to be a call from said central office.

6. The method of claim 1 and wherein confirming if the call answered within the data access time is a call initiated from the central office comprises sending a coded confirmation signal out over said telephone lines and then monitoring said telephone lines for a return coded acknowledgement signal from the central office.

7. The method of claim 6 and wherein said meter reader and said central office each include a modem and wherein said coded signals are the transmitting carrier signals of the modems.

8. The method of claim 1 and wherein isolating said subscriber telephone from said telephone lines comprises electrically disengaging said subscriber telephone from said telephone lines.

9. The method of claim 1 and wherein answering calls received during said data access time comprises coupling a fixed resistance across said telephone lines simulating an off-hook condition.

10. The method of claim 9 and wherein answering all calls received during said data access time includes detecting the presence of a ringing signal over said telephone lines prior to placing said fixed resistance across the telephone lines.

11. The method of claim 1 and wherein isolating said telephone from said telephone lines during said predetermined data access time if said subscriber telephone is not in use includes monitoring said subscriber telephone continuously for an off-hook condition.

12. The method of claim 1 and wherein transmitting said data from said meter to said central office includes converting said data to a form suitable for transmission over said telephone lines.

13. A meter reader adapted to be connected at a telephone subscriber station in series between the telephone lines connected to the subscriber station and a subscriber telephone and coupled to a meter at said subscriber station for use in transmitting data signals from said meter over said telephone lines to a central office on a call initiated by said central office, said subscriber telephone at said subscriber station including a ringing device, said meter reader comprising:
a. means for selectively isolating, said subscriber telephone from said telephone lines during a predetermined data access time, b. means for detecting a ringing signal to said subscriber station during said data access time indicating an incoming call, c. means for answering said call, causing thereby said ringing signal to terminate, d. means for ascertaining if said call is from said central office, and e. means for transmitting said data signals to said central office, if said call is from said central office.

14 . The meter reader of claim 13 and further including clock means adapted to initiate and terminate said data access time.

15. The meter reader of claim 13 and further including means for generating a ringing signal for activating said ringing device in said telephone if said incoming call is not from said central office.

16. The meter reader of claim 13 and further including off-hook detector means for detecting if said telephone is placed off hook.

17. A meter reader adapted to be connected at a telephone subscriber station in series between non-dedicated telephone lines and a telephone and coupled to a meter at said subscriber station for use in transmitting data signals from said meter over said telephone lines to a central office on a call initiated by said central office without substantially interfering with normal telephone service said telephone at said subscriber station including a bell, said meter reader comprising:
a. a microprocessor, b. telephone isolating means operable in response to control signals from said microprocessor for isolating said telephone from said telephone line for a predetermined data access time, c. ring detecting means coupled to said telephone line for detecting ringing signals to said telephone during said data access time and sending a signal in response thereto to said microprocessor, d. call answering means for answering incoming calls during said data access time, e. transmission means for transmitting data signals from said meter over said telephone lines, f. ring generator means for generating signals for activating the bell an the telephone at the subscriber station and simulated side tone signals during said data access time, and g. off-hook detector means for detecting an off-hook condition.

18. A meter reader adapted to be connected at a subscriber station in series between a telephone line and a telephone at a said subscriber station and coupled to a digital utility meter at said remote station for use in transmitting digitally encoded data signals from said meter over said telephone line to a central office in response to a call initiated by said central office, said telephone at said subscriber station including a ringing device, said meter reader comprising:
a. a microprocessor, b. a telephone isolating device responsive to signals from said microprocessor for selectively isolating said telephone from said telephone line for a predetermined data access time, c. a ring detector for detecting a ringing signal indicative of an incoming call when said telephone is isolated from said telephone line, d. means for ascertaining if said incoming call is from said central office, e. an answer call device responsive to signals from said microprocessor for causing an incoming call to be answered during said data access time when said telephone is isolated, f. transmission means for transmitting data and status signals between said microprocessor and said central office if said call is from said central office, and g. an off-hook detector for detecting an off-hook condition.

19. A data sensing and collection system comprising:
a. a central office, b. a plurality of subscriber stations, and c. a telephone line connecting said central office to each one of said subscriber stations, d. said central office including a computer having a telephone dialing mechanism, e. each of said subscriber stations including:
i. a telephone having a bell, ii. a meter reader connecting said telephone to said telephone line, and iii. a source of digital data which is to he read coupled to said meter reader, said meter reader including:
I. means for selectively isolating said telephone at said subscriber station within a predetermined data access time.
II. means for detecting an incoming call ringing signal to said telephone at said subscriber station during said data access time, III. means for answering said call so as to cause said ringing signal to terminate, IV. means for ascertaining if said incoming call is from said central office, V. means for transmitting said digitally encoded data signals to said central office if said incoming call is from said central office, VI. means for activating said bell in said telephone if said incoming call is not from said central office, and VII. means for detecting an off-hook condition of said telephone at any time.