Patent GB-804691-A (GB)
Title: Improvements in or relating to control units for switching systems
Inventor: HARRIS LIONEL ROY FRANK
IPC: H04Q3/42
Filed: 1953-11-30
Abstract: 804,691. Automatic exchange systems. POSTMASTER GENERAL. Nov. 25, 1954 [Nov. 30, 1953], No. 33263/53. Class 40 (4). In an apparatus for controlling the setting up of connections, each connection to be set up is allotted a time position in a recurring cycle of such positions and information relating to a connection is received and retransmitted to storage apparatus as a pulse occurring, in the appropriate time position on a combination out of a plurality of leads, the combination being indicative of the information received. General layout.-Figs. 1 and 2 illustrate a common control circuit which comprises in effect 99 registers each of which is allocated a pulse position in a cycle of 99 such positions. One such pulse source RP1 is shown, capable of connecting the control circuit to D.C. or audio leads A3, H3, A4, H4 and A5, H5, A6, H6 which afford connection to the calling and called sides of a connection as described in Specification 803,509 possibly modified by the use of common supervisory equipment as described in Specification 796,223. Of the equipment shown in blocks, U40, U45, U55, U70 and U80 or 80<SP>1</SP> are described with reference to Figs. 8, 9, 11, 10, 4 and 6 respectively, but U20, U25, U30 and U60 are not described in detail. When a call for a register is made, a register pulse train, e.g. RP1, is allocated to the call and all information concerning the call is stored by inserting this pulse in storage means common to all the 99 registers, the storage means being individual to the type of information to be stored. Thus a calling incoming line indicates its class of service, e.g. ordinary subscriber barred trunks, key sending manual board, junction from Strowger exchange &c. and these are indicated by the presence of the register pulse train one of the leads PL118 . . . PL122. These are connected to storage means TD105 ... TD111 in accordance with the facilities to be provided for these lines, e.g. dial tone, trunks barred, V.F. guard circuits, &c. Dialled digits or V.F. digits (in a 2-out-of-5 frequency code) are received by U20 (as breaks in the pulse train on lead PL102) or by U25 and emitted in the form of the register pulse train on two of the five leads PL 111 ... PL 115 whereupon they are stored in the main store U40. When sufficient digits have been received a translator U45 is called in, and digits to be translated are transferred thereto by applying the register pulse train to combinations of two of leads PL401 ... PL405. In this case there is used a cycle of 14 x 99 pulse positions which coincide with register pulse positions ; and coincidence with these and a set of " position " pulse trains, each having a recurrence period of 14 pulse positions coincident with the respective position pulse trains, is used to indicate the digital position of the transmitted digit. The translator where necessary deletes an appropriate number of the digits from the store U40 arid replaces them by translated digits transmitted over leads PL481 ... PL48H. The translator also provides further information over leads PL451 ... PL456 such as whether the call is to a manual board, fee for call, the identity of a manual board or outgoing junction and the number of digits that must be known before the call can be set up. Also leads PL471 . . . PL474 provide the information that a call is to a junction, whether the next exchange is of the Strowger type, the positions of digits to be forwarded to the next exchange, and whether the present exchange is able or not to determine the fee. This information is then stored on appropriate circulating systems and the marker U70 is seized. This sets up the connection as described in Specification 803,509. If then further digits are to be transmitted U55 or U60 transmits such digits whose values are received from the main store U40, either as dial impulses or as a two-out-of-five frequency code, in accordance with instructions previously received from the translator. Detailed description. Connection to register.- This takes place as described in Specification 803,509 with the exception of the choice of a free register. Since each register has one of 99 pulses associated with it these are applied to gate PSGI01 in which the pulses of all busy registers are suppressed and the remainder are applied to selector SEL1 for selection of one of them; the identity of the selected register is then indicated by D.C. on a pair of leads DCIL9, DCIL10 and by the emission of the pulse train on lead PIL101. The D.C. output from pulse lengthener PLM1 connected to the PSG101 output indicates whether a free register exists. The incoming and outgoing D.C. and audio leads corresponding to this register and serving to connect it to the calling and called sides of the connection respectively are connected via gates or modulators fed with the appropriate register pulse train RP1 to produce incoming pulse trains on leads PL102, PL103 (calling side, hold and audio) and PL105, PL106 (called side hold and audio) and to gate out pulses on leads PL104 (calling side) and PL107 (calling side) for demodulation to produce audio and hold signals. The incoming hold signal on H4 appears as a register pulse train on lead PL102 and this train is stored in delay line TD101 and applied to leads PL108, PL 104 to produce a backward D.C. hold signal on lead H3 which serves to release the register selecting circuits. When the marker is in use in a connection it emits the appropriate register pulse train on lead PIL701 for gating out and pulse lengthening to produce a D.C. signal on lead DCL3 as required in Specification 803,509. Class of service determination, Fig. 6.-As described in Specification 803,509, a multiplex MX2 is provided for each group, producing pulses P1 (Fig. 7) on lead PL1 indicative of circuits whose hold leads H1 are marked. For class discrimination a modulator MOD801 is inserted which may be fed with combinations of pulses P801 . . . P803 (Fig. 7). Each of these pulses has a width of twice the recurrence period of the P1 pulses in order to give the modulator time to build up. Thus PH1, Fig. 7, indicates the effect of modulation with P801 and P802 as in Fig. 6. During the establishment of the connection to the register these are gated into the common control circuit where the low-amplitude pulses are removed by the discriminator DIS801 to produce an output on PL801 as shown in Fig. 7. These are gated by pulses P801<SP>1</SP> ... P803<SP>1</SP> to triggers T802 ... T804 so arranged that each combination of operated triggers prepares a unique gate of the set PG801 ... PG805. After a delay to guard against temporary spurious opening of these gates, T805 operates to open the prepared gate to admit the selected register pulse train on PIL101 to one of the leads PL118 ... PL122 as an indication of the class of service. The release of the common control circuit by PCG4 is delayed by storing the release signal on a trigger T801 and allowing it to appear on lead PL809 only when a class of service signal appears on PL118 ... PL122. In a modification the modulator MOD801 is fed with a combination of frequencies which are detected by filters whose outputs cause the register pulse train to appear on the appropriate leads (Fig. 4, not shown). The class of service signals where possible are stored, in accordance with the facilities to be provided in circulating systems TD105 ... TD111. Thus the presence of the register pulse train in TD105 indicates that dial tone must be reverted (manual exchange and subscribers only). Similarly, TD106 is associated with a call from a manual board and TD107 with a call from a director exchange; TD108, TD109 alert a guard circuit U65 in the case of V.F. signalling from an electronic exchange and a key sending manual exchange respectively; TD110 causes N.U. tone to be reverted on receipt of certain prefixes (i.e. trunks barred); and TD111 indicates that a call is from an ordinary subscriber. Receipt of digits.-If dial tone is required the register pulse train is stored in TD105 and the train is modulated with dial tone at TM103 and transmitted to lead PLI04 whence it proceeds as an audio signal on lead A3. If the signals to be received are V.F. (working on a two frequencies out of five code) the register pulse train is passed from TD108 or TD109 to lead PLI09 to enable the equipment U25 which contains a pool of V.F. receivers one of which is taken into use on each burst of V.F. received and indicates the received digit by emitting the register pulse train on a combination of two out of the five leads PL251 ... PL255. If the digits received are dial impulses, they appear as breaks in the register pulse train on lead PLI02 and these are received by an impulse counter U20. The received digits are likewise indicated by the appearance of the register pulse train on two of the five leads PL201 ... PL205. In either case the digits are presented to the main store U40 over leads PL111 ... PL115. Registration in main store, Fig. 8-When a digit is received on leads PL 111 ... PL115, a check is made in the case of V.F. signals to see that the register pulse train is present on only two leads (or possibly three in the case of the first digit to cater for an " instruction digit " as subsequently described) to guard against spurious operation. During the application of a pulse XP401 to gate PCG415 any pulse existing on any of leads PL111 ... PL115 is admitted to the store TD415 provided it coincides with a V.F. signal indicating pulse on lead PL109 and provided it is not suppressed over lead PL419. This suppression occurs if two or three (in the case of the first digit) but not four or five of the leads carry the pulse. If the incorrect coding persists until pulse XP402 occurs, then the .register pulse train is gated to lead PL409 to initiate the reversion of N.U. tone. If the digits are received as dialled impulses the combination of three or more leads is als