US2218571A - Telephone system - Google Patents

Description

v 0a. 22, 1940. c, E BEALE 2,218,571

TELEPHONE SYSTEM Filed April 5, 193 2 Sheets- Sheet 1 Locm.

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INVENTOR HARLES Eouuuo BEALE ATTY.

Oct. 22, 1940. c, BEALE TELEPHONE SYSTEM Filed April 5, 193'? 2 Sheets-Sheet 2 v INVENTOR y EDMUND BM ATTY Patented Oct. 22, 1940 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Charles Edmund Beale, Liverpool, England, as-

signor to Associated Telephone & Telegraph Company, Chicago, 111., a corporation of Delaware Application April 5,1937, Serial No. 134,991 In Great Britain May 18, 1936 6 claims. (01. 179-71) 10 minimum of difllculty.

According to the invention in a telephone systemincluding a plurality of exchanges and provided with arrangements for time meteringfthe timing equipment is located at a central point and the metering equipment at the originating exchange is operated by alternating current sig nals transmitted over the speaking leads in series during conversation.

The invention will be better understood from the following description of one. method of'carry ing it into effect,reference being had to thefaccompanying drawings comprising Figs, 1 and 2.

Fig. 1 shows sufiicient of the trunking arrangements of a typical multi-office area to enable the application of the invention to be understood",

only the equipment involved in outgoing calls to central or so-called tandem exchange, M a main exchange, S a satellite exchange and SS .2; subsatellite exchange. Fig. 2 shows the elements of the speech transmission circuit between a calling sub-satellite subscriber and the timing group TG which is interposed between the central'exchang'e and a long junction to a distant exchange. The

comparativelyexpensivetiming groups need only beassociate'd with those routes which" merit the provision of timing facilitiesf Suff cient of discriminating final selector repeater DFSR is also shown to enable the operation of the metering 40 relay resetting group -MRRG enclosed inlthe MRRG may be added to existing exchange switches in any convenient manner while in new exchanges it may be incorporated on the switches concerned.

y Referring now to the trunking diagramFi g. 1,

an outgoing call from asub-satellite subscriber to a distant exchange will first be described. When the subscriber removes his receiver, he is connected via the linefinder LE toa discriminating final selector repeater DFSR fwhich causes thejunction hunter JH to select an incoming discriminating selector repeater DSR at the satellite exchange 5 and this in turn causes its junc- 55 tionhunter J H to select a first code selector FCS idle register controller. RC which stores the digits dotted rectangle to be'understood. The group inthe main exchange. In response to-the digits dialled, discrimination takes place in the discriminating switches with the effect in this instance that the junctions to main are retained, and the discriminating switches function only as impulse repeaters thereby preventing access to subsequent local switches at either the satellite or sub-satellite exchanges. On seizure of the first code selector, a register controller hunter RCH selects an dialled and. retransmits .them after translation in the well-known manner to actuate the first code selector and subsequent switches to route the'call over the outgoing junction to its destination at the distant exchange. A special timing group TC is interposed between the central exchange selector repeater SR and the outgoing junction and this may give facilities for discrimination, alternating current dialling and the like in addition to time metering. v p

Referring now to the circuit diagram Fig. 2, it will be understood that when the called subscriber answers, the shunt field relay D in DFSR will be operated in the well-known manner and at arma- .ture d2 it completes the starting circuit for the meter delay set. This latter piece of apparatus a distant exchange being shown. C denotes a comprises relays DA and DB which are operated by so-called, S and Z pulse cams which are arranged to supply battery pulses with a definite timev relation to two corresponding leads. Upon 30 reception of the next 5. pulse, relay DA will be operated over its lower winding and prepares a circuit at armature 11113 for relay DB which'operates afterthe appropriate time interval from the Z pulse in series with theupper winding of relay 35 l I its upper winding in series with the lower winding of relayDB for the duration of the Z pulse; During the application of the Z. pulse the metering relay, (not shown) is impulsed one or more times in known manner, according to the zone fee required, and at armature 7'! extends booster battery pulses over the P conductor to actuate the subscribers meter MTR accordingly. Atthe cessation ofthe Z pulse, relay restores and prevents any further operation of the metering relay, while relay DB remains operated in series with the junction switching relay K and the junction hunter magnet J HM since its upper winding is no longer short-circuited at armature (1123. Both relays P and K remain operated in series with the upper winding of relay DB.

It will be understood that on the reply of the wanted party a timing device in the group TG is set into operation. This device may conveniently take the form of a small self-starting induction synchronous motor drlven off the alternating current supply used for long distance dial-.

ling purposes or the more conventional uni-directional switch stepped by earth pulses at tensecond intervals may be used. 1

Towards the end of the predetermined unit conversational period it is arranged that a pippip-pip warning signal at a frequency of the order of 800 cycles is returned to the calling party by way of the generator Y and condenser QB. A short interval ensues and at the end of this period a pulse of low frequency alternating current of for instance 50 cycles is sent back by way of the generator X and condenser QA in order to operate relay AC and reset the meter relays in DFSR. The latter pulse is applied for an appreciable period which is of the order of fifty milli-sec0nds in order to ensure that the meter relays are reset properly and it is of a low frequency so as not to cause any inconvenience to the calling subscriber. Should he not desire to continue the conversation, it is necessary for him to restore his receiver during the grace period or otherwise he will be charged for a further conversational period. Relay AC is bridged across the line at DFSR in the sub-satellite exchange by way of a suitable low-pass filter F which renders the relay responsive only to the low frequency signal pulse and reduces the speech transmission loss to a minimum. The arrangement of rectifiers MRA to MRD enables an ordinary telephone relay to respond satisfactorily to alternating current whilst the full- Wave rectifier arrangement ensures maximum efiiciency. Relay AC will therefore be operated for the duration of the low frequency pulse and at armature acl it provides an earth to hold relays P 'and K and to shunt down relay DB which when it restores to normal short-circuits its own holding winding at armature db3. 'At the conclusion of the pulse, relay AC restores and relays P and K remain held from earth over armatures bl and 11123 while since relay D is still operated, relays DA and DB will again be operated in the same manner as before over the S and Z leads and will cause a further set of registrations to be effected on the subscribers meter. Preferably, during the extension of the low frequency repeat-metering pulse from the group TG, the through connection to the distant exchange will be disconnected and a holding loop will be provided to hold the distant train of switches. This ensures that all the signalling current is directed back towards the signal receiving equipment thereby maintaining the efiiciency of the scheme at a maximum. Referring again to thetrunking diagram, it will be seen that a metering relay resetting group MRRG is associated with the satellite exchange discriminating selector repeaters serving local subscribers while in the main and central exchanges the first code selectors serving local subscribers *areequipped likewise. Since the above mentioned switchesv are all equipped with similar DA and DB relay arrangements, time metering can be effected in a precisely similarmanner to that described for the sub-satellite case. It will be noticed however that with the equipment shown repeat metering will only take place on calls which pass through the central exchange.

Iclaim:

1. In a telephone exchange system having means for extending a call from a calling subscribers line in a local exchange to a called subscribers line in a distant exchange by way of a central exchange and trunk lines connecting said exchanges, a message register associated with said calling line, means in said local exchange for initially operating said register a predetermined number of times when said connection is first established, means in said central exchange for transmitting alternating current to said local exchange over said trunk line upon the termination of each unit period of time during which said connection is maintained, and means in said local exchange responsive to said current for reoperating said register.

2. In a telephone exchange system having means for extending a connection from a calling subscriber in a first exchange to a called subscriber in a second exchange by way of a third exchange over a trunk line connecting said first and third exchanges, a message register associated with said calling subscribers line, and means for operating said register a predetermined number of times for each unit period of time during which said connection is maintained, said means comprising a timing group in said third exchange adapted to periodically connect an alternating current of a particular frequency to the conductors of the trunk line in series and a metering relay group in said first exchange adapted to respond only to said particular frequency of alternating current, said particular frequency being such as not to interfere with conversation between said subscribers.

3. In a telephone system having means for extending a connection from a calling subscriber in a first exchange to a called subscriber in a second exchange by Way of a third exchange over a trunk line connecting said first and third exchanges, a message register associated with said calling subscribers line, a metering relay group in said first exchange for initially operating said register a predetermined number of times when said connection is established, and means for causing said metering relay group to operate said register a predetermined number of times for each unit period of time during which said connection is maintained, said last means comprising a timing group in said third exchange adapted to periodically connect an alternating current of a particular frequency to the conductors of the trunk line in series and means in said metering relay group adapted to respond only to said particular frequency of alternating current.

4. In a telephone system having means for extending a connection from a calling subscriber in a first exchange to a called subscriber in a second exchange by way of a third exchange over a trunk line connecting said first and third exchanges, a message register associated with said calling subscribers line, a metering relay group in said first exchange, means in said metering relay group for initially operating said register when said connection is established, and means for causing said metering relay group to operate said register a predetermined number of times for each unit period of time that said connection is maintained, said last means comprising a timing group in said third exchange adapted to periodically connect an alternating current of a particular frequency to the conductors of the trunk line in series, a relay in said metering relay group responsive only to said particular frequency of alternating current and normally disconnected from said trunk line, and means for connecting said relay to said trunk line responsive to the operation of said means in said metering relay group.

5. In a time metering arrangement for a telephone exchange system, a message register, means including a first relay and a second relay for operating said register, means controlled by said second relay for deenergizing said first relay,

time controlled means including a source 01 alternating current for short-circuiting and thereby deenergizing said second relay, and means for sequentially reoperating said relays.

6. In a time metering arrangement for telephone systems, a message register, a first relay, a second relay, means for operating said first relay, means for operating said second relay only in case-said first relay is operated, means for operatingsaid register only while both of said relays are operated, time controlled means including a source of alternating current for deenergizing' said second relay, means controlled by said second relay for deenergizing saidfirst relay, and means for sequentially reoperating said relays.

CHARLES EDMUND BEALE.

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