Patent GB-406270-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1932-08-20
Abstract: 406,270. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, BELAS, F. T., 26, Arlescourt Road, West Derby, both in Liverpool, and BAKER, G. T., Blackbrook, Caerphilly, Glamorgan. Aug. 20, 1932, No. 23394. [Class 40 (iv).] A code - translating register - controller is adapted to re-route a call in response to the ordinary busy signal in conjunction with a switch which counts the number of digits sent out and controls circuits which prevent rerouting if the busy signal is received in response to numerical digits or code digits at stages from which no alternative routes are available. The first portion of the banks of the usual control switch is used for this discrimination. At stages subsequent to the first code selector, the busy flash intermittently releases the relay in the outgoing loop in the register-controller while the tone is amplified and operates a further relay, the release of the loop relay or operation of the further relay being adapted to initiate re-routing if permissible. The rerouting control for an all outlets busy condition at the first code selector is somewhat different since the loop relay fails to operate and thus initiates re-routing independently of the busy signal. The re-routing code is determined by transferring the setting of the B.C. switch to the sending switch, releasing the B.C. switch and re-setting it in accordance cross connections between it and the sending switch. Specification 377,236 is referred to. Association of register-controller with calling line. Relays L and B pull up when the first code selector, Figs. 1 to 3, is seized, whereupon I energized to complete a circuit over K for the stepping relay G (lower) of switch ADF which hunts for an idle A-digit switch, Figs. 4 and 5. When the test wiper P finds, battery, G is shunted and K, previously inert, energizes over both windings and connects the calling line to impulse relay 1A of the A-switch while its relief relay KA holds line relay L (upper) over the + out wiper of ADF. The A-switch responds to the first digit and hunts for an idle register-controller, Figs. 6 to 9 in known manner. Switching relay 1H extends the holding circuit of L (upper) to ground over wipers 2f and 5e of sender SND and control switch CNT respectively. Normal operation of register-controller. The B and C digits are recorded on the office register BCS, Fig. 8, and the numerical digits are then sent to registers TH-U in known manner, switch U also acting as a distributer. The normal operations are not fully described, but such as are relevant to the present invention will be referred to in subsequent paragraphs. First code selector, Figs. 1 to 3. The first routing digit transmitted from OPS is repeated by L (upper) to VM, relay BA upper being now short-circuited by ground on off-normal springs N2 and on wiper 5e of control switch CNT, Fig. 7. Relay I is also released at N1. At the end of the digit, CNT takes a step to remove the short-circuit, whereupon BA pulls up in series with L (upper) and operates the rotary magnet RM, BA locking up over rotary springs NR2. If wiper P1 encounters a busy or disconnected terminal, ground over both windings of switching relay HA, or its lower winding only, operates the lower winding of stepping relay G (HA remaining inert) which connects its upper winding over switching relay HB to test wiper P2. If the outlet over this wiper is busy or disconnected, G having released, RM falls back and interaction between G and RM proceeds until an idle outlet is found. If P1 first finds an idle outlet HA operates over both windings, locks over the upper and G remains inert, but if P2 finds an outlet, HB operates in series with G (upper), locks and short-circuits G. All outlets busy. Wiper P1 is grounded over 11 h step springs S1 and battery over P2 operates HB which locks up, releases G and connects busy tone over wiper + 2 to the + ve out-pulsing lead. If re-routing is not provided, the register-controller sends the remaining digits to a disconnection and releases itself, whereupon the A-digit switch releases, relays K, KA in the first-code selector fall baok, and the busy tone is connected to the calling party. Re-routing after any code digit. Terminals 20, 21, Fig. 6, are strapped together. When a routing digit has been sent, 2SZ, Fig. 9, pulls up over 4f of SND to ground on the corresponding wiper 1a-5a of the office register BCS, short-circuits springs OPS to stop sending and releases 2IG which completes a self stepping circuit for sender magnet SNM over wiper 1f. When SND reaches terminals 14, 2IG pulls up again and SNM is stepped by springs SPS. If the first code selector finds all outlets busy, loop relay 21, Fig. 6, which is short-circuited until SND reaches terminals 15, fails to pull up and initiates re-routing as will appear later. If the busy condition arises subsequently, 2I will have operated on seizure of the group selector meeting the busy condition, but will be intermittently released by the flash battery. The tone passes to an amplifier (not shown) and operates 2BB. Relay 2RS, Fig. 9, tests for busy condition in positions 19, 20 of the sender switch over a circuit including the strap 21, 20, Fig. 6, and wiper 4f, Fig. 9, of SND. This circuit is completed if 21 is unoperated or 2BB is operated, and when SND reaches terminals 21, 2IG falls back to stop the switch and, since 2RS is operated, 2CA pulls up over both windings in series in a circuit including the strap and magnet SNM. Relay 2CA operates the re-routing control relay 2RR which locks up and opens circuits to prevent re-routing if the second attempt is unsuccessful. Magnet SNM pulls up when 2CA short-circuits its lower winding and interacts with 2G (left) to step the sender to a position determined by cross connections between bank 6a of the office register and bank 7f or 8f of the sender. When this position is reached, 2G holds over its right hand winding and releases 2CA which held during the stepping and which now releases 2SZ, 2G. The control switch CNT steps to 20th terminals over 5e whereupon the release magnet 2ZM of the office register operates over 2e in series with 2CA which stops CNT. When the off-normal springs 2N1 open, 2CA falls back and CNT takes another step to 21. In this position, 2VM energizes in series with 2CA and interacts with 2G (right) until the office register reaches a level marked by cross connections between vertical bank BCVB and bank 5f or 6f of the sender, whereupon 2G holds over rotary off-normal springs 2NR1 and the vertical bank, 2CA falls back and steps CNT to 22nd terminals to connect up rotary magnet 2RM and the office switch is rotated to a position marked over its wiper 6a and wiper 7f or 8f of the sender, relay 2G falling on the first rotary step. The re-routing position of the office register must be on a different level from the dialled position or earlier in the same level otherwise the register will stop in the original position. 2G again holds, and releases 2CA to step the control switch to 23rd terminals where 2G interacts with SNM to step the sender home, 2G being now held over SND (4f) and CNT (4e), and 2CA re-operated during the stepping, falling back to step CNT to 24th terminals. In position 23 of CNT, ground connected to forced release wire FR operates DB in the first code selector, this relay locking up and releasing the switching relay HA or HB. In position 24 of CNT, ground over 2CA on the - ve out lead operates the release magnet ZM and when the first code selector reaches normal 2CA relapses to step CNT to 25th terminals where 2RS, Fig. 9, is short-circuited, falls back, and completes a homing circuit for CNT. Relay 2IG pulls up again and starts the sending of the re-routing digits. Re-routing after a certain code digits only preventing re-routing at numerical stages and for codes not having re-routing facilities. The strap 20, 21 is omitted, and terminal 20 is connected to terminal RRC, Fig. 8. Under these conditions, a busy signal received after either of the first three digits operates 2RR to prevent re-routing, while re-routing takes place as previously described if the busy conditions is encountered after the fourth or fifth digit. If a call has proceeded without re-routing, 2RR is operated over wiper 3e of CNT in position 7, i.e. immediately after the thousands digit, to prevent re-routing at the numerical stages. Codes which have no re-routing facilities have the contacts in the 6th bank of the BC switch jumpered to terminal RRC. Completion of connection ; metering. When a successful connection has been established CNT in position 11 operates 2CO which disconnects ground from wire P to release K, KA in the first code selector, whereupon the speaking connection is completed and switch ADF goes home. The operation of D on response of the wanted party prepares circuits for delayed metering relays DA, DB which are operated in turn by the S and Z pulses and remain held in series during the Z pulse. Single, double and triple metering pulse leads are connected as required to contacts of a vertical bank as shown in the inset to Fig. 1, while the commoned contacts are connected to OR (left) the circuit of which is completed by DA and DB and which repeats the metering pulses as booster battery pulses over the release wire. Contacts of OR in the speaking leads (for connecting re-call ringing described later) are disconnected by DA. It may be necessary to control metering from the second selector in some trunking arrangements. For this purpose, all the contacts accessible to P1 in the 8th level are busied to make the switch cut over to the second wiper set, and the eighth level of the vertical wiper of the first code selector is connected to speaking wiper -1, the contacts of which are connected to the vertical wipers of the second selectors accessible over the corresponding contacts of the other wiper set, so that metering impulses connected up at the second sel