Patent GB-654852-A (GB)
Title: Improvements relating to telephone systems
IPC: H04Q3/42
Filed: 1948-02-20
Abstract: 654,852. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., and HENSLER, B.A. Feb. 20, 1948, No. 5155. [Class 40 (iv)] The normally slow-releasing dialling relay of an automatic selecting switch, which may be seized either from a distant exchange or by a locally situated register sender, is rendered fastreleasing in the latter case. The operators' positions at a manual switchboard are provided with cordless connecting circuits, Figs. 1-7, connected at their incoming ends to a multiple of distributer switches, revertive selector finders and line switches terminating long distance trunks, and at their outgoing ends to first trunk selectors. The connecting circuits at each position are centrally multipled to two sets of common points (A and B-appearances). Each register sender, Figs. 8 ... 12, is connected to two coupling switches SCA, SCB, each serving half the operators' positions to which the sender can be connected, the A and B-appearances of each position being connected to contact sets in the bank of one of the switches SCA, SCB associated with each register sender. Senders may be connected at the same time over the A and B-appearances at an operator's position to both sides of the same connecting circuit or to either side of different connecting circuits. Three classes of operators' positions are provided, viz., demand positions dealing with calls incoming over the local network, incoming trunk positions dealing with calls incoming over short distance trunks and positions dealing with incoming long distance trunk calls. The outlets of the first trunk selectors lead to second trunk selectors, Figs. 14 ... 19, which are also accessible from distant exchanges and which are provided with storage equipment individual to the outgoing trunk groups. Calls set up from trunk positions are automatically given priority of release from storage over calls set up from demand positions as is more fully described in Specification 654,848. Assignment of a connecting circuit at a short distance trunk or a demand operator's position. Incoming trunk and demand calls are directed to a call queue, each call being held on a rotary switch or distributer as described in Specification 634,828. When the operator receives a lamp indication that a call is waiting in the queue, she throws the speak key KS of a free connecting circuit to operate relay S, which shunts its own high resistance winding to prevent the operation of a corresponding relay associated with another connecting circuit, and completes circuits for relays SM and SK. SM and S open points in the balance wires wires N-, N+ so that the connecting circuit operates on a two wire basis. SK removes a termination consisting of a resistance and a condenser QA across the incoming speaking wires +, -, connects the incoming and outgoing speaking wires over pairs of leads OTA, OTB and OTC, OTD, respectively, and position keys to the operator's instrument circuit and connects the condenser QA across the leads OTT, OTA. Relay SL operates and MS follows to prepare the position relay circuit. The operator momentarily depresses the connect answer key CAK to remove the short-circuit on relay CG and a position pilot lamp PPL is lit and a start signal is sent over wire STQ to cause the distributer holding the call at the head of the queue to hunt for the assigned circuit. Relay CN disconnects the start signal and, when the distributer reaches the assigned connecting circuit relays B, TZ and the answering supervisory relay AS operate and CG releases. The engaged lamp EL lights. Demand calls connect up over wires -, +, s, p and trunk calls over wires -, +, N-, N+, s, p. Assignment of a connecting circuit at a long distance operator's position. Such a position does not include the circuits shown on the left of the dotted line in Fig. 4. The line switches terminating long-distance trunks connect up over wires -, +, N -, N+, s, tr and test-in over wire tr, whereupon TZ operates and holds, to prevent short-circuiting of the line switch test relay when B comes up. Connection of sender to outgoing side of the connecting circuit. When the operator has ascertained the caller's requirements, she momentarily depresses the send call key SCK and relay C operates followed by sluggish relay G. During the energizing period of G a circuit is completed for relay BA, providing no other sender is connected to the position, and the impulsing relay AP in the control circuit associated with the first trunk selectors is connected to the wire - of the A appearance. Relay G completes a circuit for CH, and connects earth over wire SE and the starting wire, e.g. SEA, Fig. 10, associated with the position to the chain starting circuit of the senders. The start relay SA of an idle sender operates and the coupling switch SCA pertaining to the position hunts for the marking applied over lead APA to a contact in the bank 14, and when the A-appearance is reached, test relay TA pulls up and B follows to earth the outgoing wire N+, thus indicating to the outgoing selectors that a local sender is in use. The starting earth is removed from wire SE by the operation of relay PA which completes a circuit for relay SC to connect the sender over the A- appearance to the outgoing line wires and to release SM. The sender start relay SA falls back. The sender loop is closed and a lamp STLA is lit by the operation of BA, and relay BB connects the code wires and the finish and cancel relays F, K, respectively, to the operator's key strip. The impulsing relay AP of the trunk selector control circuit operates over the sender loop and K follows to light the call supervisory lamp CSL. Relay CA signals the sender that the control circuit is ready to receive the first digit by connecting battery to wire N+, and relay SR having operated, sender relay VB pulls up. Register sender. When the sender is seized, a normally-operated slow-releasing relay C falls back to connect the start wires to the next sender in the chain and to busy the seized sender. The operator keys the digits by earthing one or more of the code wires W ... Z to operate the relevant register relays such as AW ... AZ. Eleven registers A ... L are provided, and the number of digits registered is indicated by the operation of a relay of the incoming distributer chain DCA ... DCL which also serves to connect the appropriate register to the code wires, the chain being under the control of a relay DS, operated when any digit key is depressed. If the A-digit determines the type of call, registration of this digit completes a circuit for relay LC (local call) or relay DA (trunk call) over one of the strappings cross-connecting terminals AT to ATL, ATA, ATB. If the type of call is determined by the A and B-digits, relay DB operates on the registration of the B-digit. Markings determined by the A, B and C-digits are applied to the banks D5, 6, 7, respectively of a discriminating switch D, and the operation of relay DA or DB causes the switch D to hunt until its test relay TB pulls up followed by CT. If the type of call is determined by the A, B and C-digits, the discriminating switches passes over the contacts marked by two digits to a contact connected to terminal etc, whereupon TB pulls up, and if or when the third digit is registered, DA follows and the switch hunts for the three-digit markings, and, when successful, TB re-operates followed by CT. The latter completes a circuit over wiper D8 for relay LC in the case of a local call, and in the case of a trunk call, for relays HA, HB singly or in combination, to determine after the transmission of which digit relay VF is to be operated, VF being arranged to open the D.C. sender loop and to operate DC to close a voice frequency signalling loop. The operation of relay LC or CT, providing VB is up, completes a circuit for relay S to close a low impedance impulsing loop, release VB, and to operate PM, the latter causing relay A to self-impulse. High speed relays AT, AS, AR pulsate with A, the former impulsing the D.C. sender loop or the latter the voice frequency loop, depending on the condition of VF. The impulses are counted by a chain of relays CA ... CD and their auxiliaries XA ... XC, as described in Specification 471,987, and when the operated counting relays correspond to the operated register relays AW ... AZ, short-circuiting earth over contacts of the previously-operated first relay of the outgoing distributer chain NA ... NL is removed from one side of a highspeed relay SP, which, on the next release of AS, operates, and stop relay SZ pulls up, shunts the impulsing contacts, prepares VB for operation by earthing the wire N+, operates SR, thus releasing the operated counting relays, and causes the outgoing distributer relays NA, NB to disconnect the A-register and to connect the B-register. The interdigital pause is determined either by the slowrelease period of PM or by the operation of VB on receipt of a signal over wire N + from the selector, whereupon SZ, SP fall back to release VB and to transmit the next digit. Digit transmission continues until the operated relays of the incoming and outgoing distributer correspond, whereupon relay DR is shortcircuited and releases to disconnect the impulsing relays and, provided the operator has depressed the finish key to operate relay F and release BB, thus disconnecting her digit keys, the release relay CO operates. First trunk selector, (Figs. 3, 6 and 7). The impulses generated by the impulsing relay AP on receipt of the first digit, operate a chain of marking relays CA ... CF, CP, CR, which connect test relay TA over leads m1 to the contacts in the bank W7 associated with the wanted group of outlets. At the end of the first impulse relay CK pulls up to connect a high-speed relay TX to the wire N+, which at the end of the digit is earthed by the sender stop relay S2. The operation of TX causes the selector to hunt and when successful relays