Patent GB-429848-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1934-01-04
Abstract: 429,848. Automatic exchange systems. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and COLLYER, J. E., c /o General Electric Co., Stoke, Coventry. Jan. 4, 1934, No. 298. [Class 40 (iv)] A group of switches having access to a panel-type bank are driven from mechanism, common only to the group, by individual clutches, a common control circuit also being provided. The constructional details of a group of such switches are described in Specification 429,891. In the system described, reversible motors are controlled from the common circuits which at the numerical stages comprise markers for controlling the conversational switches. The switches may be arranged on both sides of the panel and the two sides may be controlled by the same or separate control circuits, and as the motors are controlled from the common circuit, await an idle condition thereof for release except in the case of switches on both sides of a panel having one control when release (down drive) on one side may be effected during setting (up drive) on the other side. Talking battery is fed from the penultimate selectors having access to 5 groups of 20 connectors with two sets of wipers, selected by a discriminating signal dependent on the hundreds digit. The switches are provided with contacts which open the clutch circuit to prevent overshooting on reaching the limit of their travel. Call finder, Figs. 1 and 2. Line relay L on operation, marks the finder bank and energizes S which starts motor FM and energizes relay SA on the one side of the panel shown and a similar relay in the common control on the opposite side of the panel. The SA relays connect the common control circuits over the wipers of distributers FS to the preselected finders, one on each side of the panel. Both finders operate in the same manner except that one brush shaft moves up and the other down. In the finder shown, clutch magnet MF operates in series with relay X which prevents movement of the distributer. The brush shaft has two brush carriages represented by odd and even brushes MF operating over two different contact fields. fn are off-normal contacts and mf overshoot contacts. When the calling line is reached, SD or SE operates in series with cut-off relay K, short-circuits its high resistance winding to operate K, releases clutch-magnet MF and energizes the corresponding switching relay HA or HB. The relapse of the line relay releases the control circuits and the motor stops. Finders on each side of the panel are available as secondary choices to the control circuit on the other side of the panel, and are busied to the allotted FS over FS6 and a contact of CO which operates when all the primary choice finders are engaged. To prevent unnecessary hunting of the allotters, they are stopped on a contact of FS6 connected to a contact of both CO relays. First group selector, Figs. 3 and 4. Common line relay ZA pulls up and operates ZB which connects holding ground to the third wire, causes ZM to hunt for the finder-selector link until stopped by ZX which also operates ZY. As the selector may be on either side of the panel, the direction of drive of the common motor SM must be chosen according to the position of the selector and this is done by operating ZR or ZT over bank ZM1. The first digit is repeated by ZA to marker ZD and relay ZC in parallel and ZCA also operates during the trains to connect marking battery over ZD2 to the marking bank MS4 of the selector. As soon as ZD goes off normal, the clutch magnet MS operates over ZD1 and the selector chases the marker until ZQ releases the magnet at the commencement of the desired group. ZCA holds itself until the marked terminal is found and is then released by ZQ to transfer the marking by ZQ over ZD3 to the first contact of the next group in MS to limit the hunting which proceeds immediately since clutch magnet MS has been re-operated by the relapse of ZQ. When an idle second selector and common control therefor is picked up, ZSD operates over the third wire, releases MS and operates switching relay ZH. The consequent relapse of ZA releases ZB and ZY slowly to permit holding ground to be.returned from the second selector, ZY and ZR (or ZT) fall back, and the motor stops, the common control being now available to other selectors. Second group selector, Figs. 5 and 6. This is the feed selector, and YA pulls up followed by YB whereupon XA in the common control operates in series with YJ which remains inert. XB pulls up and XN hunts for the selector until XX operates over XN6 and operates XY which starts the motor PM in a suitable direction over XN1, XR being operated over XN1 or not according to the side of the panel on which the selector is located. The second digit is repeated by YA to XA and thence to marker XD and XC in parallel, and XCA pulls up to connect up marking battery over XM to XD2. The setting of the selector to the required group and consequent hunting operation proceed as described for the first group selector except that, as 200-point connectors are utilized, only five groups are provided for on the marker XD and a signal is sent forward over XD4, YM4 if the digit is even. The testing in circuit of the connector includes wipers TM2 and UM2 of the tens and units markers in the normal position, and XSD pulls up followed by switching relay YH when an idle connector is found. XA relapses followed by XB slowly. Connector, Figs. 7 and 8. Common impulse relay VA pulls up followed by VB, VN hunts for the connector until VX operates, and VY starts the motor QM in a suitable direction as described for the second group selector. The tens digit is repeated by YA, Fig. 5, to the impulse relay VA which steps the tens marker TM and operates VC. On the relapse of VC at the end of the train, VE operates over off-normal arc TM1, holds, transfers the impulse circuit to UM which receives the units digit in parallel with VC, and connects marking battery over relay VM to TM2 and the marking bank of the connector. As soon as UM goes off normal, clutch-magnet WM operates and the selector moves to the marked tens group whereupon VM releases the clutch magnet. When the units digit has been received VC, VE fall back and the marking battery is transferred to VM2, the clutch magnet being re-energized on the relapse of VM. When VM re-operates on the connector reaching the wanted line, the test circuit is completed during the release period of VC. The choice of test circuit over WM5 or WM6 and likewise of the switching relay WHA or WHB had been determined by the operation or non operation of VZ by the discriminating signal from the preceding selector. If the wanted line is idle, VSD pulls up followed by VH which holds, shunts VSD to release it slowly, connects a low resistance in parallel with VA to permit YJ in the second group selector to operate, and operates the selected switching relay WHA or WHB slowly. The connector is now held from the preceding selector, VA, VB, VX, VY in the common control fall back, the markers go home, the motor is stopped, and the common control is free. Ringing, completion of connection, metering. At the second group selector, YJ operated as described in the preceding paragraph, prepares a booster metering circuit at jj1 and applies ringing current over YF which, on reply of the subscriber, operates, connects the wanted line to the feed relay YD. The battery feed on the calling side is reversed for signalling if required, and YJ falls back slowly, the call being metered during its release period. Release. When the calling party hangs up, YA, Fig. 5 falls back followed by YB which releases the various switching relays. At the finder, Fig. 1, off-normal contacts fn operate R in the common control when free so that motor FM is reversely driven and clutch magnet MF operated to home the finder. The unsuccessful finder was homed at the first opportunity. At the second group selector, Fig. 5, off-normal contacts yn start the motor if idle, for reverse drive by operating XR if the off-normal switch is on the front of the panel or by a direct circuit if the switch is at the rear, the clutch magnet YM being operated over off-normal contacts and contacts of XR. An off normal switch on one side of the panel need not wait for the control to be idle if the control is setting a switch on the opposite side, the drive in this case being in the reverse direction for the off-normal unused switch. The homing arrangements of the first group selector and connector are similar. Busy signalling. If there is no available finder-selector link the calling party does not receive dial tone which is normally supplied over a winding of ZA, Fig. 4. If all second selectors are busy, ZQ, Fig. 4, operates when the first selector reaches the first contact of the next group and energizes ZG which disables the impulsing circuit to ZD and supplies busy tone over XA. If an all outlets busy conditions is found at the second selector, XM operates in a similar manner and energizes YG to connect busy tone to YA. If the wanted line is busy, VSD, Fig. 8, does not pull up, and consequently VEA, on relapse, shortcircuits VB which has been holding YH, Fig. 5. The relapse of YH connects up busy tone since YG has been operated.