Patent GB-331735-A (GB)
Title: Improvements in telegraphic systems
IPC: H04L12/04
Filed: 1929-08-22
Abstract: 331,735. Lorenz Akt.-Ges., C. Feb. 7, 1929, [Convention date]. Central station apparatus. - In a manual telegraph exchange a local record of outgoing messages is taken and the contacts of the two recording relays are connected in series, the said relays also controlling the emission of clearing signals. The subscribers station Tn is connected to an exchange VM by a line L, the line required by the subscriber being obtained either through a connecting line VL to another exchange or directly through the called subscriber's line, the former case being illustrated in the drawing. Calling operation. On the key RT, at the subscriber's station Tn, being pressed, the calling lamp AL at the exchange VM is lighted and an alarm AW sounded, by the operation of the relays AR and KR. The operator then inserts the plug A into the jack Kt thus operating the relay TR through the earth contact m and de-energizing the holding winding II of the relay AR so as to clear the calling apparatus. At the same time the line L is connected through the contact 4tr to the spring a2 of the jack Kl. The operator then enquires, with his enquiring apparatus, the nature of the desired connection and inserts the plug B into the jack Kl1, (in this case leading to a connecting line VL) this energizes the relay TR1 and connects the line VL to the operator's place. At the same. time the relay ER at the station Tn is energized through the following circuit earth, sending contact Sk, winding of ER, key RT, line L, contact 4tr winding I of relay RR, spring a2, plug a, plug b1, spring b3, contact 25rr1, battery, earth, a parallel circuit for winding II of the relay RR through the resistance N to earth being made at the same time. Relay ER responds and closes the circuit for the receiving magnet EM and a relay C which latter responds and energizes a retarded relay B which in turn closes a contact 2b connecting the motor M to the mains, and thus enabling the subscriber Tn to send out his message by means of the sending contact Sk, When the contact Sk is closed the relay RR cannot respond in virtue of the currents flowing in the windings I and II which are. differentially wound; on contact Sk being opened the winding I carries no current and hence the relay responds, current impulses being thus transferred to the line VL via earth, positive pole of battery, contact 5rr, spring b2, plug b, plug a1, spring a3, winding I of relay RR1, contact 13tr1, key T, line VL, or on the relay RR responding, via earth, negative pole of battery, spring d3, plug d1, plug c, spring c2, contact 5rr, spring b2, and so on as before. Thus an alternate positive and negative potential is applied to the connecting line VL, but if the desired subscriber were connected directly to the exchange VM, the spring d3 would not be connected to the battery and the impulses would be unidirectional. After the plug B has been inserted the operator presses the key T which transmits alternating current from an interrupter UL to a calling arrangement at the exchange connected to VL, similar to that at the exchange VM, whereby the winding II of the relay AR1 at the far exchange is energized and actuates the calling lamp AL1 and alarm AW1. On the desired connection being obtained transmission begins, and messages are transferred from the line VL to the station Tn over the key T, contact 13tr1, winding I of relay RR1 which is wound similarly to relay RR and has a similar action, thus making and breaking the circuit formed by earth, battery, contact 25rr1, spring b3, plug b1, plug a, spring a2, subscriber's line L, contact Sk, earth; the potential applied to the line L being unidirectional since the line L is a subscriber's line. Locally recording relays SR, SR1 are provided controlling two contacts 17sr, 16sr1, which control the circuit, for the local recording apparatus at MSt in series through the resistance W6, key T1, aforementioned contacts, battery and earth, and also for the two relays VR, VR1, the former being connected in parallel with the simultaneous recording apparatus MSt. For double current working, special relays St, St1 are provided which operate the contacts 14st, 15st1 so that the relays SR, SR1 responds in both positions through the resistances W2, W3, W4, W5 irrespective of the direction of the potential in the lines. The relay St1 in the case shown, is inoperative since the spring d2 is not connected to the battery. Relay VR1 is a retarded relay and opens the contact 21vr1 for the relay OV during transmision, while relay VR is permanently in action during transmission. Clearing operation. On the impulses ceasing for a certain period relay VR1 responds closing the circuit 0V which responds after about 30 seconds, closing the circuit for the lamp SL and the relay KR2 which actuates a relay LV and sounds the alarm KW alter a further 3 seconds. For urgent disconnection the plug B is withdrawn thus de-energizing the relay TR1 and putting earth on the line VL through the choke DR. This causes the relay, corresponding to SR, at the far exchange, to fall off, de-energizing the relay VR and lighting the lamp SL without delay, the alarm KW sounding 3 seconds later. The local recording apparatus MSt may be duplicated.