Patent GB-412260-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone or like systems
IPC: H04Q3/42
Filed: 1932-12-23
Abstract: 412,260. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., Connaught House, Aldwych, London.- (Hatton, W. ; 46, Avenue de Breteuil, Paris.) Dec. 23, 1932, No. 36410. [Class 40 (iv).] In a system in which the normal finders LF, Fig. 1, are connected to group selectors 1GS and the overflow finders OLFS can be used also as final selectors and give access to group selectors over second finders 2LF, the circuits of the second finders are identical with those of the normal finders, the subscriber's cut-off relay being operated from a second finder over the wipers of the combined switch. The final selectors FS are marker-controlled and a control circuit may be common to combined switches and regular switches. Normal finder. When a subscriber calls, his combined line and cut-off relay LK attracts its armature lk2 sufficiently to mark the line and initiate the operation in turn of the starting relays Fs, St, Bs, Fig. 2, and Ist, Fig. 4. A hunting switch ILF then hunts for an idle link under control of Ia which on operating to stop the switch locks up in series with Ib which starts an associated switch (not shown) in search of an idle register-controller. When the latter is found, It energizes Ie and the finder LF hunts for the line under control of a test relay in the register-controller. connected to wire 3. This relay on operating energizes B in the link and D pulls up and energizes Ic in the common circuit in series with E which is unable to pull up in this circuit. LK now operates fully in series with H over the test wire, bringing down the starting relays and S pulls up over the loop. Ia, Ib, It in the common circuit are released. Double-acting switch operating as overflow 1st finder; 2nd finder. When all the normal finders are in use, Bs is short-circuited by a chain circuit and 0 pulls up instead making driving circuits over leads such as ORL for the combined switches, Fig. 5, which hunt under control of their relays Rt. Each double-acting switch is associated over leads oa .. od and the circuit shown in Fig. 7 with the terminals of a 2nd finder, the circuits of which are identical with those of the normal finders. Rt in stopping the double-acting switch energizes Lh, and start relays Ofs, Ost, Obs for controlling the association of a register controller and the operation of a 2nd finder. When the latter finds the calling circuit, LK operates fully in series with Lh which holds the combined switch until the calling party hangs up. All outlets busy. If no 2nd finders are available, Obs is short-circuited and Olb pulls up instead to light an alarm lamp Bl unless one of the normal finders has become available in the meantime. 1st selector. When the 1st digit is dialled, the register-controller energizes If which shortcircuits the high resistance winding of Ic to enable E to pull up and energizes Irc, which locks. If the call is local, Ir is energized. The selector power-magnet GSM is energized over lead 9 and drives the switch which hunts in the group marked over a lead such as 12 under control of a test relay in the registercontroller. Ground is now connected to lead 10 to operate J which locks up and switches through. In this case no circuit is made over gs4. Double-acting switch operating as final selector. When the switch is seized, A in the common control circuit pulls up over the b-wire followed by Ec which energizes magnet SMT of the combined associating switch and tens marker in a self-interrupting circuit. When wiper smtc finds the calling b-wire, Bc stops the switch and A (owing to the low resistance of Bc) falls back. Cc in the individual circuit pulls up and locks in series with Fa in the common circuit. Fa energizes Fb and sends SHT home. Bc falls and when the switch reaches home, Q completes the forward loop through B which energizes Gc and then repeats the tens digit to SMT in series with I. Q falls when SMT goes off normal and at the end of the digit I energizes Ic to transfer the impulsing circuit to SHU of the units register. During the tens digit the combined switch chases the marker under control of T. At the end of the units digit I energizes P and when T also has been operated, Q pulls up again to transfer the marking potential from the tens to the units register. The relapse of T then starts the combined switch which hunts for the wanted line. This time the operation of T energizes Rs which connects a temporary earth over Bc to the wire f and energizes Ct to switch the talking circuit through to the 1st selector and release CC and the control circuit. Busy test and signal from 1st selector control circuit. When wire f is grounded Is pulls up in the register controller associating link, Fig. 4, locks up and connects Ilt to the wire f which is no longer connected to ground at the final selector but is connected over the test wire to the wanted Lk relay. If the line is busy Ilt is unaffected and busy tone is sent back over ilf2. Ringing from 1st selector control circuit. If the line is idle, Ilt pulls up, shunts a series resistance to busy the line and operate the wanted Lk relay fully and energizes Id which sends ringing tone back over ilf2 and ringing current forward over Irt. Completion of connection and release. When the called party replies, Irt causes'the relapse in turn of Irc, Ic, E, Ir, Is, Ilt, Id to restore the associating link to common service. The relapse of E completes the talking circuit and inserts L in the holding circuit over wire f and L holds J. Metering relay F is operated by one of the feed relays Sa, Sb, and locks up. When the calling party hangs up, S, B, D, H, J, L fall back and the switch goes home. Special service calls. In this case Ir is not energized from the register-controller and when J switches through a circuit is made over gs4 and not over gs5. When, at the end of the sending operation, Ie, If are released by the register-controller, Ic is held only until D is released by the operation of G over gs4 from the switch ahead. The circuit ILF is thus released since it is not required for controlling ringing. G also byepasses the feeding bridge, E being held operated over its upper winding.