Patent GB-438696-A (GB)
Title: Improvements in telephone systems
IPC: H04Q3/00
Filed: 1935-05-21
Abstract: 438,696. Automatic exchange systems. SZILARD, A., 3, Kßplßr utca, and KELETI, G., 52 /b, Aradi utca, both in Budapest. May 21, 1935, No. 14789. Convention date, May 23, 1934. [Class 40 (iv)] [See also Group XXXVIII] A subscriber unable or unwilling to answer calls in person sets apparatus at his substation whereby the arrival of a call causes a characteristic signal to be given at the exchange. This signal may be interpreted by a special operator who gives the appropriate message to the calling party or may cause the automatic transmission of a gramophone message. Any message from the calling party may be recorded at the exchange. The substation apparatus may act by varying the intensity, frequency phase or continuity of the ringing or feed current or may employ local sources of current. Normally the subscriber on setting the special apparatus disconnects his bell, but means may be provided whereby the bell may still be rung by the operator in the case of certain calls. An indicator may be provided at the substation to show that it has been called and duration of use of the special apparatus may be metered at the exchange. In the system shown in Fig. 2. the subscriber replaces his set by a circuit K, W, tuned to a frequency characteristic of one of a number of predetermined messages and this message is sent from common apparatus when a call arrives. In a modification, Fig. 3, the subscriber sets an impulse transmitter of revertive type. Several sets of common apparatus may be provided in one exchange or parts of such apparatus may be common to several exchanges. First system, Fig. 2. The switch Sr is constantly driven. When it encounters a link over which ringing current is being applied, R1 pulls up, and, if the ringing current in the called loop is of normal strength, R2 pulls up also and no effect is produced. When an absent subscriber is being rung, however, the loop current has a lower value and R only is operated. R3 then stops the switch, locks up, momentarily bridges the talking circuit to operate the ring-trip relay and then extends it to the message apparatus at N and Z, and starts the message selecting switch Wa which at each step varies the frequency of the oscillations generated by a valve Se. When the frequency generated agrees with the tuning of the circuit K, W at the substation the oscillatory current increases sufficiently to energize R4 which locks and completes the talking circuit to the operator at N and the selected gramophone at Z. The operator controls the restoration of the circuit by means of key Tr which unlocks R4, R3. Second system, Fig. 3. A subscriber on going out connects up an alternating current drop F which, when ringing current arrives connects a buzzer Su to the line. The constantly driven finder switch Sr at the exchange is then stopped by relay R1 which is operated over filter circuits tuned to the buzzer frequency. R1 locks and extends the line to R2 which pulls up over the loop in series with driving magnet M at the substation. R2 energizes the stepping magnet M2 of an indicator Sch which on operating holds R2 and short-circuits the magnet M. It also interrupts its own circuit by means not shown so that the devices Kl, Sch continue to advance in synchronism until Kl reaches a stop An previously set by the subscriber. The drop F is then automatically restored and Kl returns to normal. Restoration of the drop opens the loop so that R2 is released, M2 stops driving the indicator Sch and R3 is operated to connect the talking circuit to the operator's set N. After giving the message indicated the operator releases the indicator mechanically by means of key Tr which energizes R4. R4 unlocks R1 and locks itself until the release of R3 by the arrival of Sch in its normal position. Establishing connection with message-office independently of usual exchange circuits. The substation B may be modified as shown in Fig. 5 by the provision of switch S1 which connects up buzzer Su over resistance W1. In due course the constantly driven finder at the exchange picks up the line and establishes connection with the operator at the message position. Toll calls and other urgent messages. To guard against the subscriber's forgetting to restore normal conditions when he returns it may be arranged that the bell is not disconnected when the switch S is operated but is operated more weakly and a special signal may be given in the case of toll calls and urgent messages. Indicating arrangements at message office. As shown in Fig. 6, two lamp strips are controlled respectively by an additional wiper Sl1 on the finder and by a wiper Sl2 controlled by the subscriber's special impulse sending arrangement, the message to be sent being shown at the intersection of the rows indicated by the lamps. This arrangement enables subscribers to arrange for messages individual to themselves to be sent.