Patent GB-252244-A (GB)
Title: Improvements relating to automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1925-02-19
Abstract: 252,244. Siemens Bros. &. Co., Ltd., and Humphries, H. E. Feb. 19, 1925. Automatic and semi-automatic exchange systems; metering.-A register controller sends impulses forward to control the selectors and is itself controlled by reverting impulses which are repeated at the transmission bridge at the incoming end of a two wire trunk by the usual answering supervisory relay. This mutual control may be between individual registers and selectors, but the invention is described with reference to a code-translating register controller which has a back-stroke drive counting switch l, Fig. 4, common to all the registers, the stepping magnet CCM of which interrupts current over the b-wire at each energization to control the various impulse relays A. The numerical stepping magnets at the end of a stroke send a battery impulse over vm (or rm) and the a-wire to energize a relay- B which releases the magnet CCM, whereupon the wiper l is moved on the relay A is reenergized and the selector magnet falls back. Relay B is thus released and the magnet CCM energized to send a further impulse. This intercontrol continues until wiper l arrives at the terminal marked over a wiper of one of the registers j, k, whereupon a holding circuit is made for relay B in series with relay C which energizes a sluggish relay U, short circuits the holding winding of relay B and controls the advance of the sequence switch oca. Relay U locks up under control of relay B and disconnects the magnet CCM to prevent further impulsing. Relay B may fall back momentarily but is re-energized when the dialling relay D in the selector falls back to complete the rotary hunting circuit, and is held by battery on the a-wire of the succeeding selector after the switch-through until the dialling relay at that selector pulls up to indicate readiness to receive impulses. Relay B then falls back long enough to release relay U and the transmission of a further digit begins. As shown, the call is extended over a two wire trunk, terminating in a non-numerical switch 9 which selects an incoming selector 10. This is controlled in the same way as the preceding selectors. Subsequent digits are repeated forward by relay A in this selector and backward by the usual answering supervisory relay Y. The system comprises means whereby if a busy condition is encountered, the register controller and all switches ahead of the first selector are released. If the subscriber dials prematurely, neglects to dial any digit or dials a spare code or if a selector finds a faulty trunk or reaches a dead level, the register controller is automatically released. In all these cases but the last two, all other switches are released also and the subscribers line switch advances to special terminals to send " number unobtainable " tone. Provision is made for calls to and from manual exchanges. The register controller in addition to its ordinary function may control a relay corresponding to the usual sensitive relay in series with the answering supervisory relay to prevent metering and remove release control from the calling party. An incoming selector is described which has a transmission bridge and repeating arrangements which are effective only when the call is to terminate in the same office. If the call is for a distant office the incoming trunk is switched metalically through to the outgoing trunk and release control is given to a relay in the b-wire. Line switch, Fig. 5. This has normal terminals at both ends of the bank over both of which line relay R pulls up to start the driving magnet DMP. Holding circuits for relay R and magnet DMP are made by the off-normal wiper D until relay TP switches through. If all the lines are busy, the wipers stop on the last-but-two working terminals, relay TP pulling up over contact r3, and interrupted busy tone is fed back from BT, I. When the calling party hangs up, relay TP falls back and remakes the driving circuit. When the wipers reach their last-but-one terminals, relay R pulls up again over wiper D and completes at r2 on alternative driving circuit. On the last terminals relay TP pulls up, releases relay R and then falls back and completes the driving circuit for the remaining step to normal. If however, relay TP is released from the first selector while the subscriber is still calling, relay R does not fall back when the final terminals are reached and the switch is held, continuous tone being fed back from B.T to signal " number unobtainable." Selection of idle register controller. When the line switch seizes the first code selector, Fig. 6, line, release and dialling relays A ,V, D pull up and also relay AA which completes circuits for the driving magnet DMF and test relay TF of a switch CF which operates like a line switch to find an idle register controller, Fig. 7. Relay TF on switching through puts relay AA under control of the register controller over wire b. In the register controller, relay AX pulls up over the dialling tone transformer and the coil RCI, Fig. 6 and cuts the release relay NX into the circuit of relay TF. Since the coils RC, RC1 are on the same core, the subscriber hears the dialling tone. Relay NX locks itself and relay TF, energizes relay B over wiper ice of the in-sequence switch IC and relay U over wiper oce of the cut-sequence switch OC, wiper ccb of the counting switch CC and wiper icf of the switch IC. Registration of wanted number. When the subscriber dials, relay A controls relay AX which repeats the impulses over wiper ica to the magnets VM<1>, RM<1> of the Strowger office register 20, and the magnets 32, 42, 52, 62 of the digit registers. The series relay DX energizes relay JX at the beginning of each digit and at the end energizes the magnet ICM of the switch IC which is of back-stroke drive type over jx1. After a short interval relay JX opens this circuit and the switch takes a step. At the first step of the register 20, springs k1, k2 change over and the dialling transformer is replaced by a clean ground. The counting switch has the feature (which forms the subject matter of Specification 252,245) that it begins to control the transmission of one digit from the position in which it terminated the preceding digit. Consequently each of the digit registers before receiving a digit is arranged to hunt for a terminal marked in accordance with the setting of the preceding register. When the switch IC moves to its third position at the end of the office code, a short circuit over ice, icd is removed from relay P which pulls up over the interrupter springs 33,43, 55, 63 and energizes the magnet 32 of the thousands register. At the end of the stroke, springs 33 release relay P and magnet 32 falls back, moves the wipers one step and re-energizes relay P. This inter-action continues until wiper 30 finds ground from icd over wiper 23 of register 20 and relay P being short circuited over 30, ice is unable to pull up again. Magnet 32 then receivs the thousands digit from ax2. The remaining registers hunt in a similar manner but under control of wipers 41, 51, 61 for terminals marked over the wipers 31, 41, 50 before receiving their digit. Transmission of routing number. The arrangement shown provides for three routing digits, the value of which depends on the connections of the bank terminals of the office register with the busbars 1 to 10 and 11. These terminals are multipled to the 11-point counting switch CC and digit registers, the terminal 11 being multipled to the terminals on which the wipers cca, 30, 40 &c. are resting, the terminal 1 to the next terminal and so on. Since the counting switch has to begin a digit from the position in which it terminated the preceding digit, the jumpering at the frame X is not straghtforward. For example if 936 is to be sent for a received code of 28, the 28th terminals in the banks of wipers 21 - - 23 are connected respectively to the ninth, first and seventh bus-bars. If the routing number contains fewer than three digits, the terminal engaged by wiper 21, and if necessary that engaged by wiper 22, are jumpered to the wire TE. Where this has been done, the relapse of relay JX at the end of the office code energizes relay C over jx3, TE 21, oca, 71. The stepping magnet OCM pulls up and at 71 releases relay C whereupon it falls back itself and moves the wipers oca - - occ one step. If the wiper 22 also is jumpered to TE another step is taken in a similar way. Transmission begins when the sequence switch IC moves to its fourth position after the registration of the thousands digit. Wiper icc releases relay B and after an interval, relay U falls back and energizes the magnet CCM of the counting switch CC over u3, b1, nx1 icf. At the end of the stroke contact 73 removes battery from the outgoing impulse wire b, the first selector takes a step and sends back a battery impulse over the wire a to energize relay B as described in a preceding paragraph. Relay B releases the counting switch magnet which moves the wipers one step, and completes a circuit for relay QX which has not had time to fall back since the opening of the circuit by relay U. When contact 78 closes, the selector stepping magnet releases relay B and the magnet CCM pulls up again and sends a further impulse. This mutual control proceeds until the switch CC finds the terminal marked over 71, oca, 21 (22 or 23) whereupon relay B is provided with a holding circuit over cca, icb, B(2), C. Relay C energizes relay U which locks up independent of C, completes the original circuit over u5 for QX and energizes magnet OCM of the switch OC over a2 c1, b1, icf. Magnet OCM releases and is released by relay C and the wipers take a step. Relay B(2) is made sluggish by a short-circuit a4 and holds up long enough to ensure the complete building up of the flux in relay U. The relapse of the dialling relay in the selector puts battery on the wire a to hold relay B energized during h