Patent GB-260029-A (GB)
Title: Improvements in telephone systems
IPC: H04Q3/58
Filed: 1925-07-17
Abstract: 260,029. Standard Telephones & Cables, Ltd., (formerly Western Electric Co., Ltd.), (Roome, F. A., and Stevens, C. E.). July 17, 1925. Automatic and semi-automatic exchange systems.-The hunting movement of a selector is counted off by a register which prevents the selector, if all the lines in the wanted numerical group are busy, from continuing to hunt in a succeeding group. The register may be the same that controls the numerical setting of the selector. The invention is illustrated with reference to a system in which a toll connection is established from a jack J, Fig. 1, through a link circuit, Fig. 2, and group and final selectors, Figs. 5 and 6, of the rotary power-driven large capacity type. The four digits of the wanted number are written down successively on the operator's key-strip, Fig. 1, and transferred by strong and weak + and - currents in the a and b wires to relay groups such as Aar - - Adr in the register, Figs. 3 and 4, which also comprises a relay chain, shown at the foot of Fig. 4, for counting off reverting impulses. The group selector is arranged to send back impulses to this chain during hunting as well as in its numerical movement, and as soon as the number of hunting steps exceeds the number of lines in the wanted group the chain causes the connection to be released and a signal given to the operator. Provision is made in the register for translating the wanted number to a non-decimal basis. The operator is able to control the selectors by momentary applications of ringing current, and can release an existing connection to establish the toll call. During the establishment of a connection tell-tale signals (continuous, flash, flicker, or group-flicker) are transmitted to the operator's cord lamp SL by a system of marginal relays in the test circuits. Connection to idle group selector and register. When a finder PF, started by relay Asr, finds the jack J, relay Jtr energizes Rsr which shunts it (so that the starting relays Fsr, Asr relapse) and starts the switch PR. When this switch finds an idle register, relay Rtr energizes Gsr, which shunts it, and relay Rhr, Fig. 3, drives the sequence switch R to position 4, closing a circuit over resistance Rs and the wiper c to energize relay Tfr which starts the switch PG. When this switch finds an idle group selector, relay Ttr energizes relay Htr which shunts it. Relay Tgr, Fig. 5, is energized and energizes Rlr, Axr. Registration of number. The two keyboard wires are now connected each to a polarized and a marginal relay Sor, Scr and Sbr, Sdr, and when a key is pressed certain of these relays are energized and energize corresponding relays Aar - - - Adr which lock up in series with relay Par. This relay becomes energized when the key is released, and in conjunction with relay For brings a second group of relays Bar - - Bdr under control of the next key depressed, and similarly the 3rd and 4th digits are recorded on relays Car - Cdr and Dar - - Ddr. Relay Ddr locks to ground through cam J, the others lock in series with Pbr, Pcr and Zur. Numerical setting of group selector; translation; release of keyset. The energization of Pbr, when the second digit has been recorded, drives the switch R to position 6 and closes a loop fundamental circuit through relays Glr. Fig. 5, and Osr, Fig. 3. Relay Glr drives the switch R1 to position 2 and energizes the trip spindle magnet P2. The reverting impulses from commutator INT2 are repeated by relay Osr through a path determined by the record on relays Aar - - Adr to a selected point in the counting chain Ecr, Tcr, which biulds up until relay Tcro is energized, which opens the fundamental circuit and drives the switch R to position 7, whence it is driven at once to 8 by relay Zur or Ddr if all digits have been recorded. The counting chain is unlocked in passing. The circuit through wiper g is now opened, de-energizing relays Rtr, Gsr, so that a circuit is closed for relay Lhr in series with relay Tor, Fig. 1, which disconnects the keyset and de-energizes relays Jtr, Rsr. The register guard relay Rhr remains locked over the wiper f in series with a lamp RL. Meanwhile the opening of the fundamental circuit has also deenergized relay Glr, Fig. 5, which drives the switch R1 to position 3 and then again becomes energized in the fundamental circuit and drives the switch R1 to position 4, in which the brush carriage magnet P1 is energized and an impulse is sent back by commutator INT1 for each terminal passed. It is assumed that the trunks accessible to each set of brushes of the toll group selectors form 5 groups of 6, so that for different values of the 2nd digit the brushes must be numerically set to terminals numbered as follows : 2nd digit 9. 8. 7. 6. 5. 4. 3. 2. 1. 0. terminal 1. 1. 7. 7. 13. 13. 19. 19. 25. 25. This translation is effected by appropriate connections from the contacts of the relay groups Bar - - Bdr and by arranging this group to energize a relay Ohr if the digit is 5, 4, 3 or 2 and to energize relays Ohr and Sgr if the digit is 1 or 0, whereby the chain is made to perform one or two complete preliminary cycles. Thus for example, for digit 1 or 0 the chain builds up first from Ecr10 (11 steps), then from Ecr9 (10 steps) and finally from Ecr3 (4 steps). The relay Osr repeats the reverting impulses first over a front contact of Ohr to Ecr10. The energization of Tcr0 at the 11th impulse removes a short-circuit from Ehr which unlocks the whole chain except Tcr10, Ecr10 and energizes Tfr, which de-energizes Ehr, Sgr and locks itself. The following impulses are therefore repeated over front contacts of Ohr, Tcr10 to Ecr9. The energization of Tcr0 at the 21st impulse again energizes Ehr, which now locks up and short-circuits Ohr, and the remaining impulses are repeated over a back contact of Ohr and front contact of Tfr to Ecr3. The previous openings of the fundamental circuit by TcrO have been momentary and without effect on the selector, but the next energization of TcrO drives the switch R to position 9¢ (unlocking the chain and the relays Tfr, Thr) and unlocks relay Glr, Fig. 5, which drives the switch R1 to position 6. Hunting; release if all trunks are busy. Relay Glr is energized over cams E, G and again energizes magnet P1 to rotate the. brush carriage. Reverting impulses are sent back as before, and are repeated by relay Osr over cam F to build the chain from Ecr 8. The 7th impulse, which signifies that no free trunk could be found, energizes Tcr2 which connects battery direct to the wiper e to energize a marginal relay Bdr', Fig. 2, which locks in parallel with Lhr and de-energizes all relays in the link circuit, so as to release the register and group selector. If, however, an idle trunk in the wanted group is found, relay Gtr is energized over cam I and de-energizes Glr to stop the selector and to drive the switch Rl to position 8, in which the fundamental circuit is extended to relay Flr in the final selector. The fundamental circuit is transiently opened at cam N to de-energize relay Bsr, Fig. 3, which energizes TerO to drive the switch R to position 11. Numerical setting of final selector; release of register. The trip-spindle and brush-carriage movements are controlled by the tens and units relay groups Car - - Cdr and Dar - - - Ddr, and if the setting of the hundreds relay group Bar - - Bdr represents an odd digit (signified by the relay Bar being energized) ten steps are added to the units movement. In this case the relay Ohr is energized when the switch R is in position 13 (over front contacts of Zur, Bar and cam G) so that the chain is first built up from Ecr10 (11 steps). The chain is then unlocked as before described except Tcr1, Ecr1 which now remain locked over cam O, so that one step is subtracted from the further operation of the chain. If, however, the units digit is zero (in which case only the relay Ddr is energized in the units group and relay Zur is not energized) there is no circuit for relay Ohr and the impulses are repeated over a back contact of Ohr, cam P, back contact of Zur and front contact of Bar to Ecr10 ((11 steps). On the completion of units selection the switch R goes to position 1, de-energizing relay Tfr, Fig. 2, so as to disconnect the register, and the switch R2, Fig. 6, goes to position 7, opening the incoming test circuit to de-energize Gtr, Fig. 5, which energizes Glr, which locks itself and drives the switch R1 to position 12, and is then unlocked. Supply of ringing current. A short application of ringing current by the operator energizes relays Acr, Srr, Rcr, Fig. 5, of which Rcr locks up, so that on the relapse of Acr, Srr the switch R1 is driven to position 13. Relay Rcr is unlocked, Glr is transiently energized over cam E and locks itself through cam G to the a-wire, and cam K is transiently opened to unlock relay Flr, Fig. 6, which drives the switch R2 out of position 7. A test circuit is closed as the switch R2 passes position 8 and, if the wanted line is free, relay Ftr is energized and locks to the incoming test circuit, so that relay Flr, which is transiently energized over cam E in position 9#, finds no locking circuit and relapses again and the switch R2 goes on to position 13, taking ground off the incoming a wire at cam M to unlock relay Glr, which drives the switch R1 to position 16. Further applications of ringing current by the operator now cause relay Rcr to project ringing current in a circuit R, M, b and a lines, G, J, L. In the non-ringing intervals, when relay Rcr is de-energized, the called line is connected over cams P, Q to relay Tsr, which is energized when the called subscriber answers and disconnects the relay Rcr. Establishing the toll call to a busy line. If the line is busy, relay Ftr is now enerenergized, so that relay Flr finds a locking circuit over cams G, K to the incoming test wire, and holds the switch R2 in position 10, the s