Patent GB-337393-A (GB)
Title: Improvements relating to telephone systems
IPC: H04M5/08
Filed: 1929-07-29
Abstract: 337,393. Siemens Bros. & Co., Ltd., Christian, D. A., and Moore, A. T. C. July 29, 1929. Semi-automatic and manual exchange systems. -In systems using alternating current for the transmission of supervisory &c. signals over long junction lines, alternating current is sent back over the junction line during the establishment of the connection except when conversation is to take place i.e. when the operator ahead throws her listening key or when the called subscriber replies. The invention is described with reference to a two-way junction between manual offices and a one-way manual-automatic junction in which the alternating current is connected up as the result of a call, and to a two-way junction between manual offices and a two-way manualautomatic junction to which alternating sources are normally connected at both ends, the removal at one end constituting the calling signal. The signal receiving apparatus may be of the kind described in Specification 335,035. Manual-manual junction, Fig. 1, in which the alternating current is connected up to make a call. Sleeve relay CO of the calling jack OJ energizes K, L which are followed by G which connects up the tone generator VO. 1AR at the incoming end thereupon releases 1ARB which after a short interval lights the calling lamp CL<1> in series with IE which lights the busy lamps EL<1>. Sleeve relay 1J of the answering jack 1J<1> energizes 1G which sends back tone current from VO<1> to operate AR at the 1st office. ARA falls sluggishly operating X which locks up and releases G to disconnect VO from the junction. 1ARB pulls up again and is followed by 1Q which locks up. When the operator throws her listening key, 1Y releases 1G to disconnect the tone generator VO<1>. AR falls and ARA energizes T which bridges the talking wires to operate the calling supervisory relay in the outgoing cord circuit (not shown). When the listening key is restored 1Y falls and releases the distant supervisory relay. When the called subscriber replies, 1Y and consequently the supervisory relay in the distant cord circuit are operated and when he hangs up, they fall back. When the calling operator withdraws the plug CO, K, L remain held by X which is held by ARA, and G connects up the tone generator VO. 1AR releases 1ARB. 1Q falls but not before 1P has operated and locked itself to disconnect the retard RD and so release the answering supervisory relay in the incoming cord (not shown). When the answering operator takes down the cord 1J falls releasing 1G, 1P. On the disconnection of VO<1>, ARA at the calling office is operated again and X, G, K, L fall back. On the disconnection of VO, ARA is operated again and IE is released extinguishing EL<1>. If the answering operator clears first, 1G is energized over a contact of the sleeve relay and the calling supervisory relay is operated in thedistant cord. Manual-automatic junction, Fig. 2. The tone generator GR is connected to the junction by F. which pulls up over a talking wire when the plug is inserted. At the automatic end, L pulls up and then the line and release relays A, V, the latter connecting up the tone generator GR1 to operate S at the manual office, S energizes M which locks up. Dialled impulses are repeated by F and consequently by L and A. During dialling D at the manual and G at the automatic office improve the impulsing circuit by disconnecting the repeater coils. When the called party replies Y cuts off the tone current, and S falls at the manual end operating N which gives the answering signal to the cord and removes tone from the line releasing L at the automatic end. R then pulls up, locks under control of V. If the wanted party is busy, Y follows the flash impulses. The first operation operates N as in the case of the reply signal, but the subsequent relapse operates S which energizes P which locks up and connects busy tone and flash on BT to the tip of the jack. N falls back on operation of S sending tone current forward to operate L which releases A to release the switches. V falls back followed by S at the manual end. N pulls up and disconnects tone current from the junction and L at automatic end falls. When the operator clears E, F, P, M, N fall back. Busy flash is connected up also if the automatic party hangs up before the call is cleared. Manual-manual junction, Fig. 3, with tone currents normally connected up. When a plug is inserted in the calling jack OJ, K, Y, G pull up and tone generator VO is cut off. At the answering end, 1AR falls energizing 1ARA which lights the calling lamp CL<1> and connects the junction through to the answering jack IJ<1>. On the insertion of the answering plug 1CO puts out the calling lamp, answering supervisory relay in the cord (not shown) is operated in series with 1RD, and when the listening key is thrown 1Y operates 1G to cut off the tone generator VO1 releasing AR at the calling end. ARA then operates the calling supervisory relay (not shown). When the answering operator restores her key, VO<1> is connected up again and ARA falls releasing the supervisory relay. The reply and hanging up of the called party control the supervisory relay in the same way. When the calling operator clears K, Y fall followed by G. 1AR releases 1ARA and the supervisory relay falls back. Manual-automatic junction, Fig. 4, with tone currents normally connected up. The calling jack sleeve relay CO disconnects the answering jack and Y energized over a talking wire cuts off the tone generator VO. At the automatic end 1AR falls energizing 1ARA which starts the line switch or prepares the selector over the lower talking wire. Dialled impulses are repeated by Y, 1AR. Q remains operated (e.g. by off normal contacts) during impulsing and disconnects the repeater coils at the manual end while ID disconnects those at the automatic end. When the called party replies, 1Y disconnects the generator VO<1>. AR at the manual end falls energizing ARA which connects battery over RG to the a-wire to operate the calling supervisory relay. When the called party hangs up RG is disconnected releasing the supervisory relay or alternatively if he is busy the flash impulses are repeated by ARA to the supervisory relay. When the answering operator clears CO, Y fall back at her end and 1AR pulls up at the automatic end releasing 1ARA and the selectors. When the jack at the automatic end is plugged 1CO, IY disconnect the selector and remove tone current from the junction. RA falls and ARA lights the calling lamp. When the manual operator plugs in the answering supervisory relay (not shown) pulls up, K marks the junction busy and when she throws her listening key, Y cuts off VO so that 1AR falls and 1ARA operates the calling supervisory relay (not shown). On restoration of the listening key Y falls back and the supervisory relay at the other end is released. Appropriate signals are sent in a similar manner when the called party replies and when he hangs up, and when the automatic operator clears a signal is sent in the other direction.