Patent GB-279923-A (GB)
Title: Improvements in telephone systems
IPC: H04M3/40
Filed: 1926-07-06
Abstract: 279,923. Telephon-Apparat-Fabrik E. Zwietusch & Co., Ges., Frischke, M., and Schiffmann, K. July 6, 1926. Semi-automatic exchange systems.-A toll operator can extend a call through a group selector either to an operator equipped with amplifying cords or to an operator with non- amplifying cords. The amplifying cords are double-ended and are plugged into the calling and wanted toll lines, the calling toll line being switched direct to the plugged jack so that the speaking connection does not pass through the group selector. The non-amplifying cords on the other hand are single-ended, with a plug for the wanted toll line only, and the speaking connection passes through the group selector. In both cases the control of ringing current and supervision of the call are exercised by the toll operator, who remains connected over the group selector, and who can also listen in to detect amplifier defects and can call the cord operator to set them right. The operations of the two operators concerned in a call (e.g. the throwing of keys, insertion of plugs &c. )are signalled to one-another bv lamp signals. If a wanted line is busy, as shown by an indicator, the cord operator may nevertheless plug into it, in preparation for its falling idle, and tone is thereby connected to its test multiple to warn other operators from doing the same. The circuits of a toll operator are shown in Fig. 2, of an amplifying cord in Fig. 3, and of a non- amplifying cord in Fig. 4. The circuits of calling and wanted toll lines are the same, and one of them is shown at the top of Figs. 2, 3. The jack Fkv2 is provided for amplifying cords and Fkv1 for non-amplifying cords. Connection through amplifying cord. Ringing current arriving over a calling toll line energizes relay ARS1, Fig. 2, which locks up and lights lamp ASL1. The toll operator throws keys ES. AS, unlocking ARS1, energizing R, H, R2, R1 and C1 (Fig. 3), and connecting up her head-set Abfr. She takes a group selector ZGW into use by pressing a key KOT and dials a digit to cause it to seize an idle amplifier cord, Fig. 3. The cord relay A is energized and light ASL2. The cord operator throws keys AnS, MS to connect her head-set Atf to the group-selector a and b wires and to energize D, which locks itself and extinguishes ASL2. Interrupted buzzer tone and battery goes back from Su 1 to the toll operator, so that she gets an audible signal until she restores key ES, whereupon H is de-energized and relay S2 is brought into circuit to flash SL2. The cord operator inserts plugs VS1, VS2 into the jacks Fkv2 of the calling and wanted toll lines. Relay SR is energized by plug contacts Stu, and lights BL2. Relay C2 of the calling toll line is energized over the c terminal of plug VS1 and closes a flashing circuit over wire 3 for lamp BL1 at the toll operator's position, but relays R3, Z in series with C2 are not energized. Over the c terminal of plug VS2, relay P1 is energized in series with R3, and C2, U (in parallel) of the wanted toll line. Relays U and R3 switch the wanted toll line through the network LV to the jack Fkv 2. Relay P1 energizes P2, HS and is itself disconnected. Relay P2 locks itself in the c circuit of plug VS2 and relay HS locks itself in series with S2 so that SL2 glows steadily before the toll operator. The toll operator again throws keys ES and momentarily key FT to short-circuit relay C1 of the calling toll line, which brings relay U in parallel with C2 so as to energize U and also R3 and Z. Relays U and R3 switch the calling toll line through the network LV to the jack Fkv 2. Relay Z lights the amplifier VT, extinguishes BL2, and energizes DR1, DR2 to connect the plugs VS1, VS2 through the amplifier, The re-operation of key ES again energizes relay H, which unlocks HS. Ringing the calling and wanted toll lines. The toll operator throws keys ES, RS1, RS2 so as to energize relays H, E but not relay R2, since this relay is differential and circuits are now closed for both its windings. Circuits are closed from sw2 to the a and b wires of the group selector to energize WR2, WR7, which short-circuit DR2, DR1 and throw ringing current on the wanted and calling toll lines. Supervision of amplifier by toll operator. During conversation the toll operator, by throwing key ES, can connect her head-set to the a and b wires of the group selector, a circuit being closed by relays H, R2 from sw1 over the b wire of the group selector to energize relay HLT (but not WR7) which energizes RW1, RW2 to connect the amplifier VT through a repeater VU across the a and b wires. If there are noises in the amplifier the toll operator operates a flashing key FLT which energizes a relay FL (but not WR2) over the a wire, in series with a holding winding of relay H, to light lamp RL. The cord operator throws keys AnS, MS to connect her head-set Atf to the repeater VU and to energize P1, which cuts resistance w10 into the circuit of FL and H so as to de-energize these relays and flash the lamp FLKL before the toll operator. After the amplifier has been adjusted the keys AnS. MS, are restored, the lamp FLKL ceases to flash, and the key FLT is restored. Release. Ringing-off current from either of the terminal exchanges energizes relav RR1 (or RR2) which energizes HS in series with WR2 (or WR7). Relay WR2 (or WR7) transmits ringing-off current to the other exchange, and relay HS locks itself in series with S2 which lights SL2 as a clearing signal before the toll operator, who opens key KOT to release the group selector and cord. The relapse of relay A lights ASL2 and de-energizes D, Z, DR1, DR2, P2 and the relays R3, C2, U of both toll lines, which are thus immediately freed. The cord operater removes the plugs VS1, VS2. Wanted toll line busy: line prepared for waiting call. If the wanted toll line is busy as a calling line at a toll operator's position, its relay C1 is energized and the engaged signal SZ is operated. The cord operator tests the busy line and, if she finds no buzzer tone on the jack Fkv2, inserts the plug VS2, energizing relay C2 but not P1, because the circuit of relay U in parallel with C2 is opened by C1. Owing to the non-energization of relay P1, buzzer tone is sent back from Su1 through the group selector to the toll operator of the waiting call and her lamp BL1 is flashed over circuit 3; uuzzer tone from Su2 is connected to the c terminal of jack Fkv2 to warn any other cord operator that the line is not only busy but prepared for a waiting call; and lamp BL2 is lit in the waiting cord. When the existing connection is released, relay C1 relapses and permits P1, P3, U to become energized, BL2 is extinguished, and the prepared call is completed as in the case of an idle line. If the wanted line has been made busy by the plugging-in of a cord, its engaged signal 52 is energized by relay C2, and the relay P1 of the testing cord is shunted (until the existing connection is released) by relay P2 of the occupying cord. Connection through non-amplifying cord. When the cord, Fig. 4, is seized by a toll operator's group selector, relay Au lights ASL3 and the cord operator throws keys AnS to connect her listening circuit Abf. Relay Du extinguishes ASL3, and interrupted buzzer tone and battery is sent back from Su3 to the toll operator. Relay SRu is energized to light BLu when the plug VSu is lifted, and the insertion of this plug in the jack Fkv1, (top of Fig. 3) of an idle toll line energizes Pu1, C2, U. Relay U switches the toll line to the jack Fkv1 directly (not through the network LV). Relay Pu1 energizes Pu2, Pu3, HSu. Relay Pu2 disconnects Pu1 and locks itself to the c terminal of plug VSu; relay Pu3 extinguishes BLu; relay HSu locks itself in series with WR4 (which does not energize) and S2, Fig. 2, so that SL2 glows steadily instead of flashing. The toll operator, observing this, throws keys ES, RS1, RS2, whereby ringing current is thrown on the calling line from springs 2 of RS1, relay H is energized in series with R2 to unlock HSu, and a circuit is closed from sw1 cover the a wire of the group selector to energize WR4, which throws ringing current on the wanted line. At the end of conversation, ringing- off current energizes ARS1, Fig. 2, to light ASL1, or RRu, Fig. 4, which energizes HSu which locks in series with S2, Fig. 2, to light SL2. The toll operator opens key KOT to de-energize relay Au, Fig. 4, which unlocks all relays except SRu in the cord and toll line to set the latter free. Lamp ASL3 is lit and the cord operator withdraws plug VSu. The operations in preparing a waiting call are similar to those when an amplifying cord is employed.