Patent GB-796223-A (GB)
Title: Improvements in or relating to control apparatus for communication systems
Inventor: HARRIS LIONEL ROY FRANK
IPC: H04Q11/04
Filed: 1953-06-15
Abstract: 796,223. Automatic exchange systems. POSTMASTER GENERAL. June 14, 1954 [June 15, 1953], No. 16459/53. Class 40 (4). In a system in which trunks have characteristic pulse positions in a recurring series of such positions, arrangements for providing these trunks with signals such as supervisory or metering signals, comprise signal transmitting systems having pulse storage means capable of storing combinations of the pulse trains indicative of the trunks to which the signals are to be applied and means for feeding the pulse storage means over a common path with the necessary pulse trains. The pulse storage systems may be of any type, e.g. cold cathode tubes each associated with a particular pulse train or magnetostrictive delay lines, or as described in the detailed description mercury delay lines. Fig. 1 illustrates a lay-out to which the invention is applicable and shows a group GRP1 of circuits, of which CT1 is one, provided with a transmit and a receive highway GT1, GR1, each circuit modulating a pulse provided by the coincidence of pulses on two pulse train carrying leads PDL1, PDL2. The group is provided with a common supervisory circuit SUP1. The various supervisory tones to the subscribers of Group GRP1, and subscribers to which they are connected are provided over PL71, PL70, respectively. The circuit also provides over lead PHL5 signals for holding a connection between the calling and called subscribers. The circuit receives off-hook signals over GT1, GR1<SP>1</SP> from the respective ends of the connection and also signals indicative of the receipt of " answer tone ", i.e. tone received from a succeeding exchange signalling the reply of the called subscriber, by circuit BPF1, over lead AT1. All the signals consist of pulses (modulated if necessary) in the time positions utilized during the setting up of the call to the circuit CT1. The circuit SUP1 is also fed over lead PIL9 with pulses used for establishing a connection between the calling subscriber of the group and a register. Lead PL20 is fed with pulses fed to the modulator/demodulator circuits connecting called subscribers to the group highways at a time when the called circuit is selected for connection by a marker. Lead PL90 carries the pulse to be used for connection of the called circuit to the calling circuit, being either from leads PL20 or PIL14 according as the call is or is not between subscribers of the same group. The unit is also provided with D.C. marking leads indicative of the supervisory functions it has to perform. Thus GML1, GML2 respectively indicate that busy and NU tone must be reverted to a calling subscriber; GML3 that a called subscriber must receive ringing current; GML4 that the connection must be on a calling party release basis; GML5 ... GML8 by being marked in different combinations, that one out of 15 possible fees is to be charged. When a marker MKR1 is taken into use it emits D.C. on lead DCL60 and also if circuit CT1 is to be called a corresponding lead ML1 is marked in the multiplex MX5 associated with the group. The multiplex pulse output is pulse lengthened to produce an inhibiting potential for gate SG61 whose output feeds lead GML2. If the number received in the marker is not in use, no output is received from MX5, so that GML2 receives D.C. potential to indicate that NU tone must be reverted. The output of MX5 is also connected to gate PSG59 whose inhibiting lead is provided with pulses indicative of all busy circuits in the group. If the wanted circuit is busy no pulses appear on its output so that no inhibition is placed on gate SG60 and D.C. now passes to lead GML1, indicating that busy tone must be reverted. Signals on GML3 ... GML8 may be provided as a result of called number and class-of-service information held by the register to which the marker MKR1 is connected. In one embodiment. Figs. 3 and 4 (not shown), separate circulating systems are provided for each of the facilities required, each circulating system carrying a pulse train indicative of the connection requiring the facility. In a second embodiment, Fig. 5, economy in delay lines is effected by using them in combination, each combination representing a facility; and also by using some delay lines of longer delay time so that several trains of pulses may be accommodated in one circulating system. Thus the delay lines TD105 ... TD109 have a circulation time of 6 times the pulse repetition period. This time is divided into three periods, each period being allotted to a different group of circuits so that these delay lines are common to three groups, the circuit shown in the upper part of the Figure being associated with the first group. Each of these latter periods is divided into two sub-periods, each representing a different facility. For this purpose three group pulse trains GP1 ... GP3 and two facility pulse trains FP1, FP2 are provided as shown in Fig. 6, which also shows a channel pulse train CP1. In the equipment associated with the first group, delay lines TD101 ... TD 103 are used to control tone sending and have a circulation period equal to the pulse repetitior time. TD101 is used to indicate, by the presence or absence of a pulse train whether the line is a calling or a called line. TD102, TD103 are used for sending busy and NU tone respectively to a calling circuit and for providing ringing tone and answer tone to a called circuit. TD102, TD103 are used in combination to provide meter tone. In the common equipment at times FP1, TD105 and TD106 are used to remember that the called subscriber has answered and to control the sending of answer tone, and TD107 ... TD109 perform releasing functions. At times FP2, TD105 .. , TD109 perform metering functions. Delay lines D110, D111 are used to transfer information from times FP1 to FP2. Busy tone, NU tone and ringing. If the circuit is a calling circuit its pulse appearing on PIL9 is recorded in TD101 and if the called circuit is busy marking on GML1 admits the train also to TD102. Coincident pulses from these two sources pass through gate POG101, for modulation by busy tone at M61 whose output is reverted to the calling subscriber over PL71. Similarly NU marking over GML2 admits the calling pulse to TD103 and coincident pulses from TD101, TD103 are modulated with NU tone at M62. When a called subscriber is to be rung a marking on GML3 admits the called subscriber's pulse train on PL20 to TD102. The output of the latter, modulated by interrupted ringing tone, is forwarded over lead PL71 to the called party's line circuit, which is of the type described in Specifications 722,173 or 722,174, where it is converted to interrupted ringing current. During each burst of ringing current, the subscriber's line circuit reverts its pulse train over GT1 to gate PCG93 which passes it to the modulator M64, fed by ring-back tone, for backward transmission over PL70 to the calling subscriber. When the called party answers, his line circuit reverts a continuous pulse train which is passed by gate PG93 which is only opened during the interruptions of the ringing tone. The output of PG93 feeds the suppression lead of gate PCG63 to delete the pulse train from TD102, so tripping the ringing. Called party answers. When the called party answers, his pulses, received over GT1, are fed by PG93 to gate PCG105, which is opened by GP1 pulses to admit a GP1 " version" of the called party's pulses to gate PCG114 which is opened by FP1 pulses to pass a GP1/ FP1 version to the circulating system TD105. The output of TD105 gated by FP1 pulses at PCG113 passes to PCG74 which is opened by PX pulses at intervals greater than 200 ms., these pulses being sufficiently long to admit any pulses present in the circulating system. This permits the pulse in TD105 to be stored in TD106. Whilst these pulse trains are in both TD105 and TD106 they produce an output pulse train from PCG115 which is fed via the group gate PCG106 to TD103. Pulses from TD103 are modulated with answer tone at M65 for backward transmission over PL70. The circulation of TD103 is maintained via PSG104 except when pulse GP1 is present when it must be maintained via PSG107 during the FP2 period and by reinsertion from PCG115 via DM103 during the FP1 period. If metering information is held in the present exchange, however, an FP2 version of the pulse will be present as explained later on lead PL84 to suppress the pulse in TD103 so that no answer tone is sent. This moreover removes the inhibition on PSG109 so that during the next FP2 period the pulse from PCG115 is applied to suppress the circulation from TD105 at PSG108, so preventing any further insertion of the pulse into TD103. In the event of no metering information being present answer tone is sent until the occurrence of the PY pulse which passes the pulse via PCG86 to the suppression gate PSG108 to stop the circulation in TD105. Incoming answer tone passes straight, through the exchange on a tandem call. Moreover, the resulting pulses on AT1 are fed via DM101 to the common equipment in the same way as local offhook pulses from GT1 with the same results. Metering. The FP1 versions in TD105, TD106 are combined in DM102 and delayed by D110 to form FP2 versions of these pulses. GP1 versions of the called subscriber's pulses on PL90 are fed to gates PG101 ... PG104 controlled by markings on the metering indication leads GML5 ... GML8 and FP2 versions of these pulses are formed in gates PCG123, PCG125 ... PCG129 and recorded in the circulating systems TD106 ... TD109. The outputs from these are gated out at times FP2 in gates PCG122, PCG124 ... PCG128 and are applied via DM64 to lead PL84 for reasons explained above. Coincidence of the pulse on PL84 with that emitted by D110 at gate PCG87 also causes the insertion of an FP2 version of the pulse in TD105 during the next PA pulse. The pulse train is also applied to gates PCG80 ... PCG83. These are fed with pulse trains P