Patent GB-281381-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1926-08-31
Abstract: 281,381. Automatic Telephone Manufacturing Co., Ltd., (Automatic Electric Co.). Aug. 31, 1926. Semi-automatic and manual exchange systems; party line systems; metering.-In a call distributing system, calls are distributed to preselected trunks at the various operators' positions in turn. cord, circuits used for completing the connections being associated with the preselected trunks over backwardly-hunting switches. A calling line A, Fig. 1, is extended by a line switch C to a trunk R preselected by a master switch M, Fig. 3, and leading to an operator's position. An idle marker S' preselected by a switch S<2> then hunts for the trunk R, a pilot lamp is lighted to indicate to the operator the number of waiting calls, and trunk tone, is connected to the calling line. When all waiting calls have been dealt with, a distributing switch S<3> picks up the marker S' and causes the calling line to be extended to the operator's headset O, Fig. 4; the number of markers S' is equal to the maximum probable number of waiting calls, and as they are connected in the same order in the banks of the switches S<2>, S<3>, calls are extended in their order of origination. When the, marker S<1> is picked up, the trunk tone is disconnected and an operator's common call lamp is lighted, a restricted service lamp also being lighted if the calling line is not permitted toll calls. The operator tests the wanted line with the plug of an idle cord E, Fig. 2, and if the line is idle inserts the plug and momentarily depresses a common frequency key corresponding to the frequency of the bell of the wanted party on the party line, thereby initiating ringing, causing a finder F to connect the cord E with the trunk R, and causing the switch S<3> to connect the next waiting call to her headset. Failure to depress properly the ring- ing key causes the operator to receive a guard tone. If the wanted line is busy, the operator presses a common busy key, busy tone is connected to the calling line, and the next call is connected up. In the case of a reverting call, the operator gets a reverting tone when testing, and she extends the call to a special operator. When the calling and called parties hang up, the automatic switches are released, and both lines test idle so that they can receive and originate calls before the operator takes down the cord. If an operator is called by a faulty line, she depresses a common fault key, which causes fault tone to be applied to the multiples of the line, gives an alarm and causes the next call to be connected up. Separate exchange meters are operate to record the numbers of completed and uncompleted calls. Connection of calling subscriber to manual operator. When the subscriber A, Fig. 1, removes his receiver, line relay 13 of the line switch C energizes the pull-down coil 19, which connects the calling line to line relay 40 of the preselected trunk relay group R, and de-energizes relay 13. Relay 40 connects trunk tone to the calling line at armature 46, energizes the holding winding 17 of the line switch, and connects battery to conductor 210 to energize the starting relay 215, Fig. 3, of the master switch M which advances the plungers of all the associated line switches to the next idle trunk in well-known manner. The locking magnet 213 energizes a relav 214 which disconnects common conductor 211 to prevent the operation of anv line switch before the master switch comes to rest. Relay 40 also grounds a common wire 253 to energize the starting relay 236 of a marker S<1> preselected by the marker distributor S<2>, and removes ground from wire 230 leading to the multiples of the relay group R in the markers. The marker S' hunts in the normal manner for the ungrounded test contact of the relay group R, and when this is reached, switching relay 235 de-energizes relay 236, before the relapse of which wire 230 is momentarily grounded to energize relay 42, which locks up and grounds wire 230 to hold the relay 235 and mark the relay group busy. Relay 235, (1) at armature 237 grounds the contact of the marker S' in the bank B<3> of the marker distributor S<2> to cause the latter to move to the next idle marker, (2) grounds wire 245 to light a lamp L<4> of a bank, which indicates to the operator how many markers are in use and, therefore how many calls are in waiting, and (3) grounds the common starting wire 246 of the set-up control switch S<3> and removes ground from the contact associated with the marker S<1> in its bank B<5>. If no other call is in waiting, the switch S<3> immediately hunts for the marker S<1>, but if other markers hold waiting calls, nothing happens, since relays 262. 264 are already energized and the circuit of the line relay 263 is open. When the waiting calls have been dealt with and relay 264 relapses, the line relay 263 pulls up and the switch S<3> hunts for the marker S<1>. As the idle markers are preselected in rotation by the marker distributor S<2>, and as they are connected in the same order in the bank of the call assigner S<3>, they are dealt with in the same order as they are originated. When the marker S<1> is reached, between the response of switching relay 264 and the relapse of relay 263, the conductor 231 is momentarily grounded over wipers 260, 233 to energize relay 43, which locks up and grounds the wire 231 to hold relay 264, and energizes a switching relay 45, which extends the calling line to the operator's head-set O. Fig. 4, over conductors 300, 306, disconnects trunk tone from the calling line, and grounds lead 304 to light the operator's white call lamp L<3>. Extension of call by operator; ringing wanted subscriber on party line. The operator takes up an idle cord E, Fig. 2, tests the wanted line in the usual manner, and if it is free inserts the plug p<1> in the jack J<1> and momentarily depresses a common ringing key K<2> - - K<5>, Fig. 4, corresponding to the party desired. All the keys K<2> - - K<5> are arranged to complete a circuit over wire 341 for a meter N<1>, which registers the calls dealt with, for a switch relay 136, and for the holding winding 188 of the called party's line switch C', but according to which of these keys is depressed, one, none, or both of two relays 132, 133 is energized over leads 342, 343 and locks up to connect up a generator G<1> - - G<4> of the appropriate frequency. If the operator fails to depress properly the ringing key, the relay 136 and the holding winding 188 are not energized, and guard tone is transmitted over a circuit 185, 340, 314, and being induced in the right-hand winding of the induction coil I is heard by the operator. Relay 136 locks up, energizes a relay 109, which starts the finder F hunting for the trunk group R, and closes a circuit over wire 341 for a two-step relay 135, which only attracts its armature 158, over which it locks up; as its upper high-resistance winding is still shunted by the low-resistance meter winding 345, it does not fully operate until the ringing key K<2> - - K<5> is released, when at armatures 159, 160 it opens the initial circuits of relays 132, 133 to prevent false operation of theses relays if a common ringing key is subsequently operated in another connection. When the finder F reaches the ungrounded test wire 102, between the response of the switching relay 108 and the relapse of relay 109, a two-step relay 130 operates half-way over its lower winding, and the test wire 102 is grounded to energize relay 44, Fig. 1, which locks up and de-energizes relay 43, which de-energizes switching relay 45 to disconnect the operator's head-set and remove ground from common wire 304; the call lamp L<3> will extinguish if there are no waiting calls. Relay 43 also removes ground from conductors 231, 320, thereby de-energizing the switching relays 264. 235 of the switches S<3>, S'. Relay 235 extinguishes the lamp L<4> and removes ground from the associated contact in the bank of the switch S<3> to cause this switch to connect with the marker holding the next waiting call. Relay 130 locks over its armature 140, but still operates only half-way, as its upper winding is short-circuited by ground en the test wire, 102; it completes the ringing circuit at armatures 145, 141. On the reply of the called party ring-cut-off relay 134 energizes, locks up, and closes a circuit for back-bridge relav 131, which locks and completes a locking circuit for the lower winding of switching relay 136. Disconnect signals. When the calling party hangs up, relays 40, 44, 42 relapse and restore the relay group R to normal condition, the removal of ground from the release wire 24 releasing the line switch C, and the removal of ground from the release wire 102 causing the complete response of relay 130, Fig. 2, and the relapse of relay 108 and the release of the finder F. The relay 130 now lights a disconnect lamp L<1> at armature 139. On the called party hanging up, feed relay 131 de-energizes and removes a shunt from the lower winding of relay 136, the two windings of which are now included in series with the holding winding 188 of the line switch C<1> over the sleeve contacts to cause the called line to test idle to other cords and to release the line switch C<1>. Both the calling and called parties are also able to initiate calls before the operator takes down. When the operator removes the plug p<1>, relays 136, 135, 130 de-energize and the cord circuit E is restored to normal. Premature release. If the calling party abandons the call before the reply of the called party, relay 130 operates fully, lamp L<1> is lighted, and the ring-cut-off relay 134 is energized over armature 142 to disconnect ringing current. Called line busy. In this case test relay 307, Fig. 4, is energized over wire 340, tip of plug p<1>, and sleeve of jack J<1>, and closes a circuit over the left-hand winding of the operator's induction coil I, which induces a busy click in the operator's receiver. The op