Patent GB-279565-A (GB)
Title: Improvements in automatic and semi-automatic telephone circuits
IPC: H04Q3/00
Filed: 1926-07-30
Abstract: 279,565. Standard Telephones & Cables, Ltd., Searle, A. M., Wright, E. P. G., and Baker, J. H. E. July 30, 1926. Automatic exchange systems.-The invention is described with reference to a system of 5 100- line offices arranged in a chain. The first digit operates a group selector which takes into use a local connector or a repeater such as that shown in Fig. 1. If the repeater is seized over a level denoting an adjacent office, i.e. over the wires P1, -T, +T, it acts subsequently merely to repeat the remaining two digits to the distant incoming selector which acts as a connector on all its levels but one. If, however, the repeater is seized over wires P2, -S. +S (from another level), one of the finder switches belonging to a pair of register controllers hunts for it and subsequently, by its position determines the route code to be sent out. The two numerical digits are recorded on a two-motion switch, Fig, 3, associated with the repeater. This switch also functions in known manner as a local connector and is released for this service when the numerical digits have been sent by the register controller. Incoming calls arrive over the same junctions, e.g. -J, +J and pass over -B, +B to an incoming selector which sends back ground to relay B which marks the repeater busy. As mentioned above, this selector acts as a connector except on one level over which it seizes repeaters such as that shown over their wires P1, - -T, +T, energizing relays A, B, Q. Relay A repeats subsequent digits over the junction, a dialling relay C shunting the impedance I during impulsing. Selecting register-controller. When the repeater is picked up over P2, +S, -S, relay X pulls up, locks itself, short-circuits its lower winding to allow relay A to pull up and energize relays B, Q, and grounds the wire SW. The finders can hunt only one at a time, that shown, Fig. 2, having preference. If the other one is hunting at this time, Its relay UB disconnects the starting ground on SW from the register controller shown. When it stops however, the relay UB falls back and relay C completes a self-interrupting circuit for the magnet which drives the wipers A1 - - A6 until the calling repeater is reached, whereupon relays S, T pull up in series. May S releases relav U and diverts the start wire to the other register controller. Relay T locks itself and relay S switches the in-impulsing circuit over +C, -C to the associated connector, connects the junction to the out-impulsing wires +D, -D grounds the wire M to operate the busy relay G in the connector as soon as the second digit begins and releases relay X to unground the start wire. In the register controller, relay LC pulls up in two steps over springs LS and connects up relay CC over the springs MS. Relay CC pulls up in two steps and completes a sell-interrupting circuit for the magnet SCDM which moves the sender control wipers SC1 - - SC4 one step, releasing relay CC. Transmission by register-controller. The parallel relay E when the units digit begins energizes (over PR, PR2) relay L, which, provided the other register controller is not sending at this time as indicated by the position of its relay LB, drives the sender control switch to 3 over SC2. If the route code is to consist of one digit only, the terminal on which wiper A5 rests will be jumpered to DCO and a circuit will now be made over SC2 for the magnet SCDM which drives the switch to 5. For other numbers of digits, wiper A5 will be on a terminal jumpered to a terminal in the first quadrant of one of the sending switches SSA, SSB. From position 3, the relay CC is connected up again over the springs MS and on pulling up connects the driving magnets SSAM, SSDM to the springs MS. At the first step of these switches, the pick-up relay SA renders impulses from springs LC effective on the trunk, and when one of the sending switch wipers encounters the terminal jumpered to wiper A5, the stop relay SZ short-circuits the loop springs and releases relay CC whereupon the sending switches go automatically to the end of the first quadrant, relays SA, SZ fall back in succession and the sender control switch moves to 4. The value of the second digit is determined by the jumpering of the A5 terminal in the second quadrant of the sending switches. When the sender control switch moves to 5 at the end of the digit, the wiper A6 is connected up and the third digit if any (or the only one) is sent in accordance with the jumpering of the A6 terminal in the first quadrant. When the sender control switch moves to 6 the sending switches are advanced one step over SC4, SA-15, LC-8 and then to normal over their off-normal banks. Relay SA is re-energized in parallel with the driving magnets over wiper SC4 before relay SZ has had time to fall back and consequently no digit is sent during this movement. When normal is reached, relay SA allows the sender-control switch to move to 7. In this position and position 8 the marking ground on wiper SC2 is connected over PR2 to an extra wiper of the connector. The terminal on which this wiper rests is jumpered to terminals in the first and second quadrants of the sending switches and accordingly two more digits are sent out in the same way as the 1st and 2nd digits of the route code. Release of register controller and connector. In 9, the sender control switch energizes relay CO, which releases relays S, T, whereupon relays L, LC fall back. On the relapse of relay S the sender control switch makes two homing steps and on the relapse of relay L a further step to normal. The relapse of relay T switches the calling line through to the junction over condensers QA. QB, and frees the connector. Alarm and busy signals. If, owing to spring failure, wiper SC2 is still in position 1 when relay L is energized, relay PA (which is common to both register controllers) locks up and operates an alarm on PL, and relay CO unlocks relays S, T and grounds wiper +D over LC-18 to energize relay SX which sends back busy tone from BT and releases relav Q to free the junction for incoming calls. If a register-controller has not been appropriated when relay C first pulls up, relay SX pulls up over X-12 to send the busy signal and cut off relay Q.