Patent GB-216554-A (GB)
Abstract: 216,554. Automatic Telephone Manufacturing Co., Ltd., and Gillings, C. Jan. 30, 1923. Addition to 194,427. Automatic exchange systems.-A system of the kind described in the parent Specification, in which the first three letters of the name of the wanted exchange are dialled to a register controller which translates them into the series of digits necessary for routing the call to that exchange, is modified to comprise the following features.-(1) The register-controllers are divided into ten groups, an idle register-controller of a wanted group being picked out by an idle group selector RS, Fig. 5, which is connected to the calling line by a finder switch FS and afterwards responds to the first exchange digit. If all the register controllers of a wanted group are busy, an attendant's supervisory lamp L, Fig. 1, associated with the outgoing trunk to the first exchange selector E', is lighted and the switches RS, FS are restored. (2) Means are provided for lighting the lamp L and releasing the registercontroller if any of the groups of connecting switches required for a connection are all busy. (3) If the calling party neglects to dial, dials less than the full number of digits, or unduly prolongs the interval between dialling the first and second or the second and third exchange letters, or if the retransmission of the digits by the register-controller is delayed, the lamp L is lighted and the attendant by inserting a plug P<1>, Fig. 3, into a jack J can listen in on the calling line, and if necessary either release the switches FS, RS and the register controller or himself control the setting up of the wanted connection. (4) If a subscriber's line becomes permanently earthed. or short-circuited, the attendant is signalled and the line may be made non-selectable. Selection of an idle register-controller of the group corresponding to the first digit dialled. As soon as a calling subscriber's line-switch has selected an idle trunk a, b, c, Fig. 4, the line relay A energizes the slow-release relay B, which grounds the test wire c, disconnects earth from the test conductor c', lights the supervisory lamp L, and grounds the common starting wire SW. The starting relav A<1>, Fig. 5. of the first idle non-numerical finder switch FS is therebv energized, completing a series circuit for the switching relay B<1> and the stepping magnet M, and connecting the junction point between them to the test wiper TW. The finder switch FS now rotates in well-known manner until its test wiper TW engages the unearthed terminal 20, upon which the switching relay B<1> locks energized in series with a supervisory relay E, Fig. 4, which locks up over its armature 22, opens the circuit of the lamp L, and connects dialling tone from the lead DT, Fig. 5, to the trunk conductor b. The switching relay B' de-energizes the starting relay A', connects the starting wire SW to the next finder switch at armature 11, and energizes a stop relay C, Fig. 4, over the earthed conductors 17, c<1>. The stop relay C locks up and removes earth from the starting wire SW. The first digit is repeated by the line relay A over circuit c, 4, 40, 36, c<1> to the vertical magnet V of the register selector RS, which operates in the manner of a group selector to find an idle register-controller of the proper group. Operation of the register-controller. The register-controller is set by the digits dialled and controls the automatic switches to set up the connection in the same manner as the register-controller described in Specification 194,580 with the following small differences. The. relays 106, 107, 110, and 111, Fig. 6, correspond to relays in the before-mentioned Specification bearing the reference numerals. Instead of the starting relays 110, 111 energizing in parallel immediately the register-controller is taken into use, the relay 110 energizes first and completes a circuit 101, 102. 103, 66, 69 for the impulse relay F, Fig. 4, which at armature 63 opens the impulse circuit to the vertical magnet V<1> of the first selector E<1> slightly before earth is connected to the impulse conductor 62 over a circuit 101, 104, 105, 59, 60. In this manner the possibility of the vertical magnet V<1> receiving a preliminary impulse is prevented. Impulses are generated in the usual manner by the impulse relay 107 which at armature 102 interrupts the circuit of relay F causing impulses to be transmitted to the vertical magnet V<1>, which steps the wipers 80 - - 82 to the desired level, in which they rotate to find an idle line. The remaining series of impulses generated by the relay 107 also interrupt the circuit of the relay F which at armature 93 breaks a bridge 91, 92, 93, 94 across the trunk conductors 85, 86. The relay G, Fig. 4, is energized during the transmission of each impulse series by the registercontroller. Release of the switches FS, RS and the register controller. When the register-controller has re-transmitted the last digit, the switching relay D locks energized and de-energizes the line relay A, causing the relapse of the relav B, which deenergizes the relay B' of the switch FS. A circuit is thereby completed for the release magnet RM of the register selector RS. The register-controller is released in known manner. Signalling attendant and release of switches FS, RS if all the register-controllers of a wanted group are busy. When the last contact set in the selected level of the switch RS is reached, busy flash current is applied from the lead BF over the cam springs 77. The application of earth to the lead 72 short-circuits the supervisory relay E, Fig. 4, which unlocks and lights the attendant's lamp L, whilst the application of negative potential short-circuits the switching relav B<1>, which relapses and restores the switches FS, RS. The operator by inserting the plug P<1>, Fig. 3, in the jack J may cut in and ask the calling party to call again, or may herself control the setting up of the wanted connection. Signalling attendant and release of registercontroller if anv of the groups of connecting switches required for a connection are all busy. Means are provided at the connecting switches for sending a busy flash current over the b trunk. The application of earth potential to the conductor 86 short-circuits the supervisory relay E over a circuit 94, 78, 79, whilst negative potential short-circuits the switching relay B<1> over a circuit 94, 78, 79, 8, h, thereby lighting the lamp L and releasing the switches FS, RS and the register-controller. Signalling attendant if calling party neglects to dial. A cam T, Fig. 5, earth a lead PL at the register selector RS every 30 seconds, so that if this switch is not moved out of its normal position a circuit 95, 96, 97 is completed for the upper winding of a marginal relay F', which partially pulls up and at armature 98 short-circuits its lower winding. When earth is removed from the lead PL this short-circuit is removed, all the armatures are attracted and a circuit is prepared for a relay G<1>, which, if the calling party has not commenced to dial in the interim, is energized when the cam T again grounds the lead PL after a lapse of 30 seconds. The relay G<1> locks up and grounds the conductor 72, thereby shortcircuiting the supervisory relay E and lighting the lamp L. The supervisory attendant may listen in on the calling line by inserting the plug P', Fig. 3, into the jack J, and by pressing the key K may ground the sleeve, thereby energizing the relay D and releasing the switches FS. RS. Signalling attendant if (1) calling party dials less than the full number of digits, (2) delay occurs between the first and second or the second and third exchange digits, (3) delay occurs between re-transmission of the digits by the register controller. The register selector RS is provided with a fifth wiper 45 which is connected to the lead 72 and earthed from the register-controller over the bank contact 54 in any of the above circumstances. The supervisory relay E is thereby short-circuited and the attendant signalled as before described. If the calling party dials less than the full number of digits, or if undue delay occurs between the dialling of the first and second or second and third exchange digits, the earth may be supplied from a register-controller pick-up relay, which is energized under these circumstances, such as the relay 205 shown in Fig. 2 of Specification 212,666, whilst if delay occurs between the re-transmission of digits, the bank contact 54 may be grounded over a contact of an alarm relay such as the relay 559, shown in Fig. 2 of Specification 212,666. Signalling attendant if a subscriber's line is permanently earthed or short-circuited. These faults are equivalent to the subscriber lifting his receiver but neglecting to dial and the same supervisory operations take place. The attendant may insert into the jack J a plug P, Fig. 2, which permanently earths the sleeve, thereby energizing the relay D which earths the test wire c and renders the line non-selectable. The Provisional Specification describes an alternative arrangement in which a hunting switch individual to the outgoing trunk a, b, c connects up an idle register-selector RS.