Patent GB-679660-A (GB)
Title: Improvements in or relating to telephone systems
Inventor: BEALE CHARLES EDMUND
IPC: H04M3/54
Filed: 1950-01-17
Abstract: 679,660. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Jan. 9, 1951 [Jan. 17, 1950], No. 1157/50. Class 40 (iv). In an arrangement for answering, at the exchange, calls to absent subscribers or for monitoring incoming calls to subscribers troubled by malicious calls, the transmission from a manual board solely of a subscriber's directory number causes any subsequent incoming calls to that subscriber's line to be routed to the manual board. As shown, Fig. 1, an operator at the manual board MB may insert her plug into a special jack to engage a group selector GS. If she then dials or key-sends the required subscriber's number, a marking selector MS is set to the subscriber's line in a bank D of the normal final selectors FS and a marking condition is applied to the line when the operator withdraws her plug. Any subsequent incoming call to the marked line via the penultimate selector PS and the final selector FS is automatically diverted to the manual board MB via finders WF, JF and a relay set JRS. The operator may then complete the connection and either allow the call to proceed normally or release the called subscriber and trace the call if necessary. The manual board MB may be at a local or remote exchange. Group selector GS, Figs. 2, 3. This is engaged over conductors TWP and relay A repeats the first digit dialled by the operator to vertical magnet VM which raises the switch to the required level where it hunts over wipers P1, P2 for an idle line to a marking selector. If none is found, 11th step springs S2 substitute busy tone from lead 11 for dial tone from lead 10. If wiper P1 or P2 finds an idle line, relay HA or HB prepares an impulsing circuit to wiper B1 or B2 and thence to the seized marking selector. Marking selector MS, Fig. 4. Magnet WSM drives wipers WS1, WS2 in accordance with the second digit to select one of the wipers W1 ... W10 which are then set bv the third and fourth digits, a relay RC in the group selector switching the impulsing path for the third digit from the B wiper to the M wiper. At the end of the fourth digit RC re-operates and applies earth to the M wiper, relays EA, PT being already energized. This brings up a relay CO in the marking selector to connect battery via a relay KD, wiper WS2, and the selected one of the wipers W1 ... W10 to the required subscriber's contact in the bank D of the final selectors FS. This battery is replaced by earth from wiper WS1 when the operator withdraws her plug to release the group selector and relay CO. The subscriber's line is now marked in the final selectors by this earth. Release of marking selector and removal of marking. If the operator repeats the above operations, a second marking selector connects battery over its relay KD to the same contact in the final selectors, and the two relays KD operate in series. A relay EB in the first marking selector is energized and completes a self-interrupting circuit for rotary magnet RMA to initiate release. The second marking selector is released when the operator withdraws her plug. One marking selector differs from the rest in having a contact eb5 and the connection shown dotted in Fig. 4. In this case, when relay CO releases on the withdrawal of the operator's plug, relay KD operates and brings up relay EB to initiate release. This selector may be used only for releasing other marking selectors and not for marking. Final selector FS, Figs. 5, 6. This is engaged by an incoming call over group selector multiple GSM and responds to the last two digits of the wanted subscriber's number in normal manner. At the end of the final digit, relays AA, AB, ACA are held energized, relay AC releases and relay AE begins to release slowly. If the final selector has come to rest on a line marked in bank D1 or D2 by earth from the marking selector MS, a relay TW operates and locks in series with a relay ST in a start circuit SR, Fig. 7, over leads 22, 23. When relay AE completes its release, relay AC re-operates and extends battery via relay TW to a conductor C connected to a contact in a bank of a finder WF, Fig. 7. Finder equipment, Figs. 7, 8, 9. A start relay ST is energized in series with TW as described above and brings up relays STA, STB in a relay set JRS. Magnet JFM drives a finder JF until wiper JF1 reaches the contact associated with the operated ST relay, where it fails to find earth so that the finder JF stops, engaging a further finder WF. A relay K operates to energize a latch magnet LM in the engaged finder WF, which is then driven by magnet DM in search of the relevant final selector FS which is marked by battery on the conductor C. If this is found by wiper S1 or S2, a relay TA operates to release latch magnet LM and stop the finder WF, whereas if it is found by wiper S3 or S4 the finder is stopped by a relay TB which also brings up a relay AHA to energize wiper-switching relay SW. In either case, relays AH, HR operate to release relays STB, STA and extend the speech conductors into the relay set JRS. Relay LA operates in series with relay D in the final selector which releases start relay ST and performs metering functions. Ringing tone is now provided from lead 24, instead of from lead 15, Fig. 5, as previously. Relays DT, LB are energized in series, lighting a lamp LP at the manual board MB, and a circuit is completed for a thermal relay BTH. If the operator fails to answer, BTH releases the finder equipment and relays D, TW in the final selector, and the caller receives busy tone from lead 16, Fig. 5. If, however, the operator answers by inserting her plug P in jack TWJ before BTH can operate, a relay L extinguishes lamp LP, line-balancing relays ID, IA are energized, and a relay CR disconnects BTH and energizes relays AS, LR to disconnect ringing tone and release whichever of the relays TA, TB has been energized. The operator is now in communication with the caller over her speech conductors 26, 27. Operator completes connection to wanted line. By closing a key KS, the operator adds a further battery potential sufficient to operate relay LC in series with L. Relays LB, DT, ID are released and a relay BS operates, transferring earth from the conductor C to the conductor T leading to the final selector FS, thereby releasing relays TW, ACA and providing a test path for relay H to the wanted line via wiper P1 or P2. The call can then proceed normally. When the operator releases her key KS, relay LC is de-energized so that LB, DT, ID re-operate and AS, LA, D are released. Operator retakes control of connection. On a second operation of key KS, relay LC reoperates to release LB, DT, ID, BS. Earth is switched back from the conductor T to the conductor C, re-operating relays TW, ACA in the final selector, and relays LA, D, STB are re-energized. The release of key KS releases relay LC, and LB, DT, AS are re-operated. Malicious call: operator releases called subscriber. A third operation of key KS again energizes LC and releases LB, DT, ID. Relay BS re-operates and earths the conductor T to the final selector, where relay H is shunted and released, thereby breaking the speech circuit and removing earth from the called subscriber's P-wire. On the release of key KS, relay LC is released to bring up LB, DT, ID once mora and BS releases. The finder equipment, Figs. 7, 8, 9, is released when the operator withdraws her plug P.