Patent GB-346368-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone exchange systems
IPC: H04Q3/00
Filed: 1930-01-07
Abstract: 346,368. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., WRIGHT, E. P. G., and HARTLEY, G. C., Columbia House, Aldwych, London. Jan. 7, 1930, No. 611. [Class 40 (iv).] In an interexchange network, the selection of a junction in the wanted direction is effected by bye-path apparatus FB, SB, Fig. 1, responsive respectively to the first, and second and third exchange digits, the second byepath SB containing discriminating means which determines whether or not a register-translator RT will be required to assist in the completion of the connection. A registertranslator is seized for every call so as to be ready if required but if not required it is released unused. Register-translators are required in the following circumstances: (1) for all tandem calls, including alternative routing via a tandem exchange when all direct-junctions are busy ; (2) for calls to callindicator manual exchanges in which case the numerical digits are converted into code impulses; and (3) when the first numerical digit arrives before the incoming selector at the terminating exchange is ready to receive it. In the first case, a code switch C in the seized register-translator is set in accordance with the complete exchange designation but in the other cases only the numerical digits pass to the register-translator. In the second byepath SB the second exchange digit operates switch R1 to mark a group of contacts on switch R3 which then responds directly to the third code digit to select a particular contact within the marked group. Byepath switch R2 selects the required group of outgoing junctions under the control of R3 and then hunts for an idle junction within the group. Meanwhile an idle register-translator has been associated with the byepath over a switch RF and if the call is one requiring to be routed over a tandem exchange the switch C is set to a group dependent on the first exchange digit this being determined by the setting of switch RF and then to a position within the group under the control of switch R3. In tandem calls zone-metering signals are sent from the register-translator to the outgoing repeater where they control the transmission of the appropriate number of metering impulses on the reply of the called subscriber. Operation of second byepath SB by second and third exchange digits ; seizure of register-translator. The byepath, Figs. 2 and 3, is seized over lead T, Fig. 3, and relays A, B, BE, operate. Relay A repeats the second exchange digit to magnet RM1 of switch R1, at the first movement of which circuits are completed over wiper rm19 for magnets RM2, RM3. Magnet RM3 continues to operate over wiper rm35 until the beginning of a group marked by wiper rml8 is reached when relay N operates over wiper rm38. The first contact in each group of outlets in the bank of wiper rm20 is connected to the contact in the bank of wiper rm31 or rm32 reached in response to the corresponding code combination, all contacts in the latter banks not corresponding to exchange codes being multipled to the next following contact which does correspond to an exchange code. Magnet RM2 thus continues to operate over wiper rm29 until a contact marked by wiper rm32 is reached when relay M operates. At the end of the digit the relapse of relay C completes, when both M and N have operated, a circuit for relay E which directs the third code digit to magnet RM3. Relay E also locks up relay JA, if operated, to discriminate between odd and even second digits, and completes a self-interrupting circuit for magnet RM1 which advances switch R1 into engagement with the selector S2 which is handling the call. Relays T, TT, then operate and the preceding byepath FB is released. During the third digit, switch R2 advances further under the control of wiper rm31 or rm32, and relay CE operates to start the finderswitches associated with idle register-translators, terminal T, Fig. 2, being marked by battery over the lower non-inductive winding of relay K. In each idle registertranslator relay A operates to connect up magnet RF, and when the calling byepath is reached, relay B in the successful registertranslator is operated over wiper rf2. At the end of the third digit, relay TM operates connecting ground over wiper rm36 or rm37 to a contact individual to the wanted exchange which is jumpered over a distributing frame DF to one of the terminals AT .. S in accordance with the class of call. Contacts which do not correspond to any existing exchange are wired to terminal DC so that relay G is operated energizing relay K which opens the starting circuit to the register-translators and connects up " number unobtainable " tone NU. Statistical metering. Meters common to a number of byepath circuits are operated over wipers rm39, rm30 to indicate the total number of calls to each exchange whilst a further meter multipled to all unused contacts indicates the number of calls to non-existent exchanges. Local call. The contact in the bank of wiper rm36 or rm37 corresponding to the local exchange is jumpered to terminal S so that relay N is operated again to energize relay R. Relay M is released and magnet RM2 again operated and switch R2 hunts simultaneously over two levels under the control of test wipers rm23, rm24. If all outlets are busy, relay M again operates over wiper rm20 and the last contact in the group and operates relay G which connects up busy tone BT and releases the register-translator. If wiper rm24 finds an idle outlet relay Q operates followed by wiperswitching relay J and relay H which short-circuits Q Relay DH energizes over the outgoing loop operating relay HH which releases the register-translator and relays A, B, Fig. 3. Relay H also closes a circuit for magnet SM of the conversational switch S2 which hunts for a contact marked in the bank of wiper sm4 by wiper rm22. When this is reached relay M operates to stop the switch and to energize relay G which operates switching relay HS. When ground is removed from wiper rm24 by the succeeding byepath, relay BE releases and the byepath SB returns to normal. Call to exchange reached only over a tandem exchange; zone metering. The contact in bank rm39 or rm30 is jumpered to terminal D energizing relays D, CI. Relay D switches over the marking connection for switch R2 causing this switch to advance to the beginning of the group of tandem junctions, and the selection of an idle junction in this group takes place in a similar manner to that for a local call. The numerical digits are repeated over wiper rf5 and relay C, Fig. 4, to magnet NS. Relay C operates relay DS and at the end of each digit except the last the relapse of relay C completes a circuit over wipers ns4 .. ns7 to operate sets of storage relays WA .. WD, XA .. XD, YA .. YD in varying combinations. When relay DS relapses a circuit is closed over wiper ns1 to move the switch NS to a sub-normal position in readiness for the next digit. The last digit remains stored on the switch NS and relay DS is maintained operated over wiper ns1 at the end of this digit. In the meantime, as a result of the operation of relay CI, relay TM has released causing ground to be connected over wiper rf8 to indicate to the registertranslator that the call is one via a tandem exchange. Relay H in the register-translator operates completing a circuit for magnet CM which advances the code switch C to one of a number of home positions dependent on the value of the first exchange digit. This selection is determined by connecting each home contact of wiper cm5 to all contacts in the bank of wiper rf4 corresponding to second byepath circuits reached in response to a particular first digit. When the appropriate home position is reached relay CA operates over wipers rf4, cm5, to stop the switch and to operate relay BB. Ground is now connected over wiper sm1 to relay CC which operates when springs ms1 are open and completes a circuit for relay CB. Impulses from springs ms1 are thereby transmitted over relay CZ, wiper rf3, and wiper rm33 or rm34 to switch RM3, and each impulse is repeated by relay CZ to magnet CM. Switch CM is thus set to a position dependent on the second and third exchange digits as recorded on switch RM3, the impulsing of both switches continuing until wiper rm33 or rm34 steps off an associated arbitrary multiple. Relay CC being released, relay CB falls back and relay CC operates again and connects springs ms1 to switch SM. The value of the routing digits is determined by jumperings between the banks of wipers cm1 .. cm4 and the sets of contacts 3 .. 12, 15 .. 24, 27 .. 36, 39 .. 48, respectively, in the bank of wiper sm2. For the transmission of each digit relay CC operates over bank sm1 in positions 1, 13, 25, 37, connecting springs ms1 to magnet SM, corresponding impulses being transmitted from springs LS over wipers rf0, rf9 and the outgoing loop. When the marked contact is reached relay SZ operates to shortcircuit springs LS and to advance switch SM to the next starting position 13, 25, 37, 49. One or more routing digits may be skipped by making jumperings to terminals 13, 25, 37 in the bank of wiper sm2 thus preventing relay SZ from releasing in these positions. The numerical digits are retransmitted in a similar manner in positions 49 .. 95 of switch SM as determined by connections to bank sm2, over contacts of the storage relay groups for the first three digits and over wiper ns6 for the last. In position 96 of switch SM relay G, Fig. 3, is operated over wiper rf1 to initiate the operation of relay HS and the release of the byepath and registertranslator. In the latter the release of relav B leaves relay H locked across wipers rf0, rf9 and the outgoing loop. When this loop is opened the release of relay H connects zone-metering terminals MA, MB to the outgoing a and b wires and earth is connected momentarily to one or other or both according to the position of wiper cm5. Shortly after the r