Patent GB-357091-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04Q3/62
Filed: 1930-06-06
Abstract: 357,091. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., Columbia House, Aldwych, London.- (Hatton, W. ; Spann, R. D. ; Rousseau, E. J. ; and Larson, F. O. V. ; 46, Avenue de Breteuil, Paris.) June 6, 1930, No. 17572. [Class 40 (iv).] Junction circuits, which can be connected with either automatically or with the aid of an operator, are multiplied over several operator's positions, the arrangement being such that when a free circuit is entered by an operator, another operator is prevented from connecting with it. The invention is described as applied to a relay-type P.A.B.X. of small capacity (10 or 20) in which local calls are obtained automatically and in which the operators are normally employed on other duties, such as type-writing, so making a liberal provision of operator's positions necessary. Incoming calls are signalled to all operators but the first to answer the call cancels all other signals, and this operator alone receives supervisory signals on the circuit. The subscribers are graded, some being barred outgoing and/or incoming junction calls and others, having full facilities, have to obtain their outgoing junction connections via an operator. Each operator has a local number and is obtained by dialling that number. When a call has been established the operator can enter the circuit only at the request of the local party and then the exchange is cut out and held by a resistance loop. Engaged circuits are marked by absence of an indicator signal when a connection to the relative circuit has been made. Local call. When the line is looped L energizes provided the register (Fig. 2) is free (L, cl, 2, c1, 6, l5, a5, t2, SMI1, a8) and locks over l4 in series with T. T marks the register engaged, by breaking the initial operating circuit, and enables S to pull up. S completes a circuit for relay P2 in the first free link circuit, and this relay operates, breaking the circuit of the other P relays and energizing P12. T is started and releases followed by S, and C2 pulls up connecting the calling instrument from earth at m1. 5 to battery at I (Fig. 2). I energizes followed by O and A, and TO operates from earth on a6 to connect dial tone to the calling subscriber. Pl2 releases. The system as shown requires one setting digit only although a larger system can be provided by supplying an additional SM switch. The calling subscriber dials the number of the wanted party and the impulses are repeated by i1 to SM1, Lm operating in parallel. When the train ceases Lm falls back, E operates and locks to Rg, and S, which re-operated when A pulled up, starts to fall away. During the slow period of S, ground is connected over s1, brush 4 of SM1 and a lead such as b to relay L of the wanted line. T operates and Rs pulls up, starting the ringing pulsing relays X and X and connecting ringing through Rg to the wanted circuit. When the called party replies Rg operates, E releases, M1 pulls up, and Pl2 reoperates completing a circuit for the called party's C2 relay to pull up. The calling and called parties are connected in parallel to the common supervisory relay N1. When M1 operated. I, 0, and A fell away, SM1 homed over a8, and the register became available for another call. Ringing is connected to the called circuit for 6-8 seconds only and if the subscriber has not answered in this time thermostat. Nb makes its front contact to operate M1 which connects the called party to the link and frees the register. If the called party should answer later, the circuit is ready for conversation. When both subscribers hang up, N1 releases followed by M1 and the operated C relays. If the called party had been engaged, one of his C relays would have been operated, and consequently T would not have energized over the test circuit. In these circumstances TO pulls up over back contacts of RC and connects busy tone to the calling party. Nb operates as before to free the register if the calling party does not clear in its operating time of 6-8 seconds. The thermostat Ha has an operating time of 20-30 seconds and this operates M1 to release the register if dialling is delayed for more than this period. Outgoing junction call obtained automatically. To ring the exchange a full facility subscriber dials the digit O setting the register to its tenth position to which leads a are connected. When Lm falls back at the end of the train E operates and T pulls up over wiper 4 in series with Je of the first free junction circuit. A parallel circuit is also completed for M1 and P12. M1 operating causes the register circuit to release and Pl2 enables relay Jcr to pull up connecting the subscriber over a metallic loop to the outgoing junction circuit (Fig. 5). Supervisory relay Js operates followed by Jm and Jb which latter relav marks the circuit as busy. When the P.A.B.X. subscriber hangs up Js releases followed by Jm. Jm closes the circuit for thermostat Jt which opens its contact after 5-8 seconds to release the junction and link circuits. Outgoing junction call completed by operator. The operator may obtain junction calls for full facility and for certain restricted out-service subscribers. One operator's equipment is shown in Fig. 6, others being connected up over other pairs of Jn, Jo relays and each operator is given an individual number. The local subscriber calls the number of the required operator who moves her key AK to position LOK to connect her telephone set to the local circuit and she takes particulars of the call required. The local subscriber may now clear and be rerung by the operator when the call matures. The attendant restores key AK and depresses a junction key JK to position HK. If the junction is free the relay Ji operates closing a circuit over contacts of all Jn and Jo relays to operate the signal SG which completes a circuit for the buzzer BU. The key JK is then moved to position LK which opens the signal circuit and completes a circuit for Jo to connect the operator's instrument direct to the exchange circuit. Jo completes a circuit for Jn which opens the operating path for all other Jo relays connected with the circuit and thus prevents another operator entering the circuit. Js operates over the outgoing loop and Jm and Jb pull up, marking the junction busy to the register. When the attendant is in communication with the city exchange the calling party is rerung as described below in connection with an incoming call. Incoming call. Ringing current from the distant exchange causes the operation of Jw which allows Ji to pull up. Ji connects battery to all signals connected with this junction and the first operator to press her relative junction key to the LK position will remove the signal from all positions and make herself responsible for the call. The position is now the same as when the operator is about to recall the local subscriber on an outgoing call. The operator throws her key AK to the RK position and the relative JK relay pulls up if no other JK relay is already operated. Over its contact 2, JK closes a circuit for Je (to a7) and if the register circuit is free Jl energizes, completing a circuit for T which energizes and allows a free link to be seized. Jl completes a circuit for R1 which opens the test circuit over wiper 5 of SM1. All subscribers with restricted in-service facilities are connected to banks of SM1 and as the test circuit is broken incoming exchange connections cannot be established. Relays P2 and Pl2 operate, assuming that the first link circuit has been seized, and Jer pulls up. At contact jcr8 a circuit is completed for Jd which connects the city subscriber to a resistance loop and Je is energized. The operator receives dialling tone and dials the number required, the dialling circuit being jd5, jp2, jo2, jo5, jp5, jd4, jcr3, ml3 winding of I. When P2 in the link circuit releases, Jd de-energizes followed by Jk, and Ja operates. The release of Jd reconnects the city subscriber to the operator, the called line being extended to Jr. When the called party replies Jr operates followed by Jp which latter relay connects the city line back to the resistance loop and the local subscriber to the operator. The operator restores her junction key, Jo releases followed by Ja, Jp and Jr, and the local subscriber is connected to the exchange circuit. Instead of waiting for the reply of the called party, the operator may, as soon as ringing tone is received, move her key JK to position HK. Jp operates connecting the called circuit to Jr and the exchange line to a resistance loop. Jo releases bringing up the signal on the operator's position. When the called subscriber replies Jr operates, releasing Jn, Ja and Jp, restoring the signal SG and connecting the two parties. Should the called party not reply the operator can re-enter the circuit by moving the junction key JK to position LK, operating Jo and releasing Jp. When the local subscriber clears Js releases, Jm falls back and thermostat Jt operates. When Jt opens its front contact the common holding earth is removed and all energized relays release. Recalling an operator on a junction call. To recall an operator, the local subscriber depresses his switchhook for a short time. The opening of the loop causes Js and Jm to release and J/ pulls up and locks. When the loop is reclosed Js and Jm reoperate and, with J/ up, the Jo relays pull up to signal the operators. One of the operators depresses her relative junction key JK to the LK position, causing the operation of her relative Jo, Jr relays and the opening of the circuit to other operators. Jn completes a circuit for Ja which reconnects the local subscriber to Jr whereupon Jp pulls up connecting the local subscriber to the operator and the city line to a resistance loop. The attendant may release the local subscriber by throwing the key AK to position RK operating Jk. As Ja is energized, Jl, Jc, C2, and Je release, freeing the link circuit, and when the key AK is restored Jk, Ja