Patent GB-719506-A (GB)
Title: Improvements in or relating to circuit arrangements for telecommunication, and particularly telephone installations having relay selectors
Inventor: SPIECKER FRIEDRICH
IPC: H04Q3/00
Filed: 1952-08-15
Abstract: 719,506. Automatic exchange systems. SIEMENS & HALSKE AKT.-GES. Aug. 15, 1952, No. 20575/52. Class 40 (4). A line of a P.B.X. group which is in use on a trunk call is marked busy to incoming trunk calls by a relay individual to the line, which relay is operated by a signal indicative of the trunk nature of the call for which the line was seized. P.B.X. lines in use for local calls may be seized for incoming trunk calls. Outgoing calls from the P.B.X. group.-These are set up in the manner described in Specification 718,838. The operation of the cut-off relay T (Fig. 2) busies the calling line for incoming calls and transfers the pilot wire mal to the next line of the P.B.X. group. Local calls to the P.B.X. group.-The set of final selection relays ER (Fig. 5) is assumed to have been seized by the calling line via path OA. Relay C31 pulls up to negative battery on wire 86, and locks up with O11 to wire 87. A free final digit setter EZE1 is associated, relays Hand K31 operating. Relay El comes up in the holding circuit of K31 but N stays down. The final three digits are then dialled and repeated by A2 to A3 in the digit setter, dialling relay V coming up for the duration of each digital train. Operation of the relevant hundreds, tens, and units relays HR, ZR, and ER connects up pilot wire mal. The operation of end-of-selection relay Wel brings up Pze1 and, providing no other selection is proceeding simultaneously, Sp2 follows. Resistance 105 is short-circuited and N operates. Assuming MA1 (Fig. 2) to be busy and MA2 free, a test circuit is completed over relay P (Fig. 5), wire mal, front T1 (Fig. 2), back T2, back AR2, back T2, relay Ka2, wire 6, back Sp1 (Fig. 3) and relay An, in which P, Ka2, and An all operate: The intermediate lines ZLt which are allotted by LO in the order ZLt 1-10 for outgoing calls, are allotted in the opposite order (viz. ZLt 10-1) for incoming calls. Assuming ZLt 10-7 (not shown) to be busy, then Qe6 (Fig. 3) operates in series with common relay G. Relay C6 follows to extend the allotting circuits. to Qe5 and Qv7 respectively. Relay Q6 (Fig. 2) comes up, whereupon coupling relay K2<SP>6</SP> operates in series with Sp1 (Fig. 3). In the final selector the response of P signals the coupling relays EK to connect through the speech wires, and removes the short-circuit of El. Relay Per pulls up over wire 153 and locks over 157 with AR2 and T2 (Fig. 2), whereupon El, K31, and P relapse and S pulls up to switch through the connection. The operation of T2 connects Ka2 to a contact chain over which locally engaged lines can be taken into use for incoming trunk calls over wire ma5, and extends mal to Ka3. Operation of S also connects V in series with the slow interrupter LU so that V operates intermittingly and connects ringing current to wire 237. When U relapses (shortcircuited by release of El) V is connected to the ringing generator RS. On the reply of the called subscriber A2, B2 pull up and N relapses to trip the ringing. Release is initiated by the calling party, T2 holding to the called loop until the called party hangs up. Night service.-Pilot wires ma2, ma3 are used to select individual lines MA2, MA3 respectively, which may be plugged through at the P.B.X. Incoming trunk traffic.-The two lines MA5, MA4 are provided for incoming trunk traffic exclusively and if they are both busy a free local traffic line is allocated by extension of pilot wire ma5 over contacts of the cut-off relays T5-T1. If all lines of the group are busy, ma5 is further extended over contacts of the trunk busy relays F3-F to seize one of the local traffic lines which is engaged in a local call. If all the local traffic lines are in use for trunk calls F1-F3 are all up and the call under consideration cannot be established. Trunk traffic line MA5 free.,-The set of final selection relays ER (Fig. 5) is seized over path FA and C31 pulls up. Operation of H then brings up Y to negative battery on wire 192, and after N has operated, P, Ka5 (Fig. 2), and An (Fig. 3) all pull up in the test circuit. The connection is completed in the usual manner. All trunk traffic lines busy, and MA2 free.- Relays P, Ka2, and An come up in the test circuit together with F2 (Fig. 2). The connection is established as before, F2 holding under control of T2 for the duration of the call to mark MA2 as busy on a trunk call. All lines busy-breaking in.-Relay FV1 (Fig. 2) is connected in the test circuit, so that P and Ka3 cannot operate, and An alone comes up. Relay El therefore remains short-circuited and X is operated, thus disconnecting S and applying a high voltage through both windings of P to the test circuit. Relays P, FU1, and Ka3 thereupon pull up followed by FUH1 (Fig. 2). Assuming the line MA3 to be in use by an outgoing call through ZLtl and that the incoming trunk call is allotted to ZLt4 (viz. 3ZLe7) by the operation of K3<SP>4</SP>, relay Per pulls up to front Qe<SP>4</SP> (Fig. 3) and holds in a local circuit (Fig. 5). The second winding of relay X is connected in parallel with C21(ii) and O1 (Fig. 4) in the set of selection relays WR1 in use on the local call, so that the current through it is not sufficient to bring down the differential relay X. The trunk operator applies negative battery to wire 228 thus bringing up B2 which extends her to the local call. She informs the parties in the local call that a trunk call requires to be connected and requests them to hang up. If they do so X falls away and S switches through in the usual way. Forced release of local call.-If they do not hang up the operator applies positive battery to 192 to bring up A2 (B2 remaining up to negative on 228). Relay H follows and applies positive battery to the speech wires 237, 238 which results in Bl in the local call relay set WR1 (Fig. 4) releasing and A1 holding up. Relay C1 (ii) is thus short-circuited initiating release of the local call; X (Fig. 5) relapses and S switches through as before. Relay FU1 (Fig. 2) falls away and, during the release time of FUH, F3 pulls up to mark line MA3 as engaged on a trunk call. Preventing local calls from being established over the trunk traffic lines.-This is effected by connecting a resistance 244 in the pilot wire ma5 (Fig. 2) to prevent the operation of P (Fig. 5) in the initial test circuit. If the caller is a local subscriber he receives busy tone. If, however, the call is an incoming trunk call X comes up and the high voltage is connected to the test circuit to bring up P; X relapses immediately and S switches through.