Patent GB-191314524-A (GB)
Title: Improvements in or relating to Telephone Systems.
Inventor: AITKEN WILLIAM
IPC: H04M5/08
Filed: 1913-06-23
Granted: 1914-06-23
Abstract: 14,524. Aitken, W. June 23. [Cognate Applications, 16,859/13, 18,349/13, 19,521/13, and 19,988/13.] Exchange systems; metering systems. - Relates to improvements in the system described in Specification 16,906/12 in which the circuits through a cord are automatically opened when one of the subscribers replaces his receiver, thus causing the plugs to be electrically inoperative so that the busy potential is at once removed from both lines, and a subscriber may at once make a second call, without waiting for the operator to remove the plugs. Several modifications are described, t h e more prominent features being (1) an arrangement by which the answering - plug is disconnected when the calling subscriber hangs up but the calling-plug is o n l y disconnected when both subscribers have replaced their receivers; (2) a supervisory system in which a lamp glows so long as connexion through the cord is completed; (3) an application of the principle of automatic d i s c o nnexion to private branch exchange switchboards; (4) improved methods of adapting the prior invention to junction line working; and (5) methods of metering completed calls automatically. Cord circuits for A-operators; manual metering. In the cord circuit shown in Fig. 1, a single relay D controls the circuits of the plugs P, P', its operating-circuit through winding 1 being temporarily closed at contact 2 of the operator's key Q, the holding-winding 11 receiving current over the calling line, disconnexion being controlled only by the calling subscriber. A lamp L glows as long as relay D is energized, and a lamp L<1> enables the called subscriber to give a clearing signal before the calling subscriber hangs up. In the cord shown in Fig. 4, separate disconnecting-relays D<3>, D<4> are used for the answering and calling plugs. The relay D<3> is initially energized over its winding 90 and contact 92 of key Q<2>, and locks up over winding 100 and the calling line. The relay D<3> energizes the relay D<4> over winding 105, thus extending the repeater F<3> to the calling plug. When the called subscriber answers, current flows through the winding 123 of relay D<4> in parallel with relay 124, which shunts out the lamp L<6>. The lamp L<7> glows throughout the connexion. When the calling subscriber hangs up, the relay D<3> disconnects the plug P<4>, and opens the circuit through winding 105 of relay D<4>, thus removing the shunt round lamp L<5>, which glows until the called subscriber hangs up, thereby opening the circuit through the winding 123 of relay D<4>, which then de-energizes, and isolates the plug P<5>. If the called subscriber hangs up first, the relay 124 opens the shunt round lamp L<6>, which glows until the calling subscriber hangs up. In the cord shown in Fig. 5, the relays D<3>, D<4>, Fig. 4, are replaced by electro-magnetically retained keys K, K', associated with the plugs P<6>, P<7>, respectively. When the operator inserts the answering-plug P<6> and depresses her key Q<3>, the keys K, K' are mechanically depressed, and the key K is held depressed by current from the battery B<5> over windings 133, 154, contacts 131, 156, and the calling line. The key K, by closing contact 159, also supplies current to the right-hand winding of key K<1>, thus retaining the key and connecting the plugs P<6>, P<7>. The lamp L<8> lights up over contacts 137, 136, 134 and the bush of the jack. When t h e called subscriber replies, the relay N<2> is energized and disconnects the lamp L<8>, at the same time closing a circuit through the winding 153 of key K'. When the calling subscriber hangs up, the key K is released, but the key K<1> remains energized until both subscribers replace their receivers. Fig. 6 shows a suitable construction of the keys Q<3>, K, K<1> and their retaining- magnets 163, 164. Figs. 4 and 5 show manuallyoperated metering-keys by which the current over the c-lead can be strengthened. Cord circuits for A- operators; automatic metering. In the cord shown in Fig. 10, separate disconnecting-relays D<5>, D<6> are used, for the answering and calling plugs P", P<13>. The relay D<5> is initially energized over its lower winding and contact 281 of key Q<6>, and locks up over its upper winding and the armature of a supervisory relay, which is energized over the calling line. The relay D<5> supplies current to the winding 296 of relay D<6>, which extends the repeater F<4> to the called line, and lights the lamp L'‹. The insertion of the calling-plug closes a circuit over the sleeve contact 315 and contact 317 for a lamp L<11>. When the called subscriber answers, his supervisory relay 306 shunts the lamp L" by the winding 319 of relay D<6>, and also momentarily grounds the slow-release metering control relay 295, the armature of which is retained in its attracted position by current over a resistance 294 and contact 292, so as to prevent a possible repetition of metering. The relay 295 momentarily closes the metering-circuit through the batteries B<8>, B<9>, operator's meter V, contacts 332, 333, 291, sleeve 289, and subscriber's meter V<1>, Fig. 12. The operator's key W provides for additional metering, if required. Fig. 11 shows a modified cord for use in systems in which a subscriber's meter is provided both at the substation and at the exchange. The sub-station meter V<2>, Fig. 12, is normally in parallel with the subscriber's telephone, but when the line circuit is completed an auxiliarv armature 350 is attracted so as to connect the meter V<2> in parallel with the condenser 353, this current not being strong enough to actuate the meter. The disconnecting-relay D', Fig. 11, is energized in the same way as the relay D<5>, Fig. 10, and completes a circuit for the meter control relay 357, which attracts its armatures 358, 361 so as to open contacts 358-359, 361-362 and to close contacts 359-360, 362-363, and also closes at contact 364 a circuit over a resistance 366 for a metering-relay 367, which is not operated bv this current. When the called subscriber replies, his supervisory relay 368 momentarily grounds the slow-release relay 367, which is then energized, the current through the resistance 366 being sufficient to keep the armature attracted. When the calling subscriber hangs up, the relay D' disconnects the relay 357, which in de-energizing closes a momentary circuit over the batteries B<9>, B<10>, operator's meter V<3>, contacts 373, 358, 359, 360, ring of plug P<14>, calling line and slow-release meter V<2>, tip of plug, contacts 363, 362, 361 to earth. At the same time, a circuit is closed over the batteries B‹, B<10>, meter V<3>, contacts 373, 358, 359, sleeve of plug P<14>, to the subscriber's exchange meter V<1>. The Provisional Specification 19,988/13 states that the subscriber's bell may be biassed so as to ring once when the meter is operated. In the modified arrangements for the sub - station meter V<4>, Fig. 13, the relay winding 390 is in parallel with the telephone, and when the subscriber removes his receiver, this winding closes the contact 395, thus connecting t h e actuating - winding 391 in parallel with the condenser. Junction-line working; operator's testing - set. In the cord for a B-operator shown in Fig. 2, the insertion of a calling-plug in the jack J energizes a relay N, which completes the circuit of the disconnecting-relay D<1>, so as to connect the repeater to the calling-plug. The relay D<1> closes the circuit of a lamp L<2> which glows during the connexion. In order that the B-operator may know that the A-operator has plugged into the jack J, and therefore that the relay D' has energized, so that the B-operator can test the called line, a relay M, energized by the relay D<1>, controls the connexion of a special tone transformer to a tertiary winding 39 on the operator's induction coil. The Provisional Specification 19,521/13 describes a modification of the system shown in Fig. 2, in which the relay N controls the disconnecting-relay D' through an intermediate relay which is used for supervisory purposes. In applying the principle of automatic disconnexion to a ringing-junction, the disconnecting-relay is initially energized over a contact of the B-operator's speaking key, and is locked over a contact of the junction line relay. Private branch exchange working. Fig. 8 shows a cord circuit for P.B.X. working suitable for use with the A-operator's cord-circuit shown in Fig. 1, in which complete disconnexion of the plugs is controlled by the calling subscriber alone. In Fig. 8 are shown the answering and calling jacks J<2>, J<3> of an exchange line, and jacks J<4>, J<5> for extension lines. When a call is received from the main exchange, the operator inserts the answering-plug P<8> in jack J<2>, and depresses her key Q<4>, associated mechanically with the disconnecting-key K<2>. A holding-circuit for the key K<2> is completed from the exchange line over the tip of plug P<8>, contact 172, winding 174 of key, contact 176, inductance 177, contact 178, relay 180, contact 181, winding 183, contact 185, and ring of plug P<8> back to the exchange line. The contact 178 is only momentarily closed, but the circuit is maintained over the contact 189 of relay 180, this contact being arranged in parallel to the contacts 178. If an extension line is required, the plug P<1> is inserted in a jack J<5>, say, thus completing a circuit through the cut-off relay 190, sleeve of plug, contact 193, and relay 196, which is not energized owing to the high resistance of the cut-off relay. When the extension party answers, a circuit from the main exchange to the extension line is completed from the exchange line, tip of plug P<8>, contacts 172, 201, 198, tip of plug P', extension line, ring of plug P<9>, contacts 208, 205, relay 203, contact 185, ring of plug P<8> and back to the exchange line. The relay 203 short-circuits the relay 180, which de-energizes, the holding-