Patent GB-180317-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M3/30
Filed: 1922-05-06
Abstract: 180,317. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Lomax, C. E.). May 18, 1921, [Convention date]. Automatic exchange systems; party line systems.-A test clerk can release one of the switches over which he has set up a testing connection without releasing the remainder, by varying the potential of a control circuit extending from his position to a relay group associated with one of the switches. The invention is described as applied to a system of 100,000 lines, divided into ten 10,000-line exchanges, in which the lines of all the exchanges are tested from one central position by one or more test clerks, to whose positions are multipled groups of trunks to each of the ten exchanges. The system includes party lines which are reached through an additional group selector, which selects a connector supplying the appropriate ringing frequency. Each test trunk terminates in a test distributor E, Fig. 2, which is controlled by the first two digits of the wanted number to select a trunk, which if the wanted line is an individual one, leads direct to a test connector H, Fig. 3, allocated to the 100- line group containing the wanted line, but which, if the wanted line is a party line, leads to an auxiliary single co-ordinate test selector F, Fig. 3, which in response to an additional digit extends connection to a test connector allocated to the wanted 100-line group. Release is controlled by a test clerk T, Fig. 1, over a metallic circuit extending over conductors 34, 35 to the line relay 43 and to two marginal relays 41, 42, at the test distributor E, Fig. 2. If the test clerk desires to release the connector H, or if the call is to a party line, both the selector F and the connector H, without releasing the distributor E, by the operation of a control key K<1>, Fig. 1, he inserts a resistance R<1> in the control circuit 34, 35, thereby causing the relapse of the marginal relays 41, 42 and the subsequent release of the switch H, or of both switches F, H. By the insertion of an alternative resistance R he may cause the relapse of the marginal relav 41 only, which interrupts the circuit of the switching relay 180 of the line switch C, Fig. 3, associated with the called line. The operation of the line switch C may then be tested. A connection may also be set up over the test switches by a complaint operator T<1>, Fig. 4, who, by operating a key K', connects her impulse transmitter S<2> across an idle trunk 250, 251 leading to a group selector D, which in response to an exchange designating digit extends connection to an idle testing trunk 32, 33 to the wanted exchange. Extension of test clerk T, Fig. 1, to a test selector F, Fig. 3, by a test distributor E, Fig. 2. The test clerk, by the operation of an exchange key K<3>, connects his test conductors 30, 31 to an idle test trunk 32, 33 leading to the exchange in which the wanted line terminates. Actuation of the key K<3> also earths the test lead 36, thus illuminating the test lamps, such as L<2>, at other test positions and marking the seized trunk busy, energizes the right-hand winding of the polarized relay 7, and at springs 14, 19 places a bridge across the control conductors 34, 35, which includes the left-hand winding of the polarized relay 7. The relay 7 does not respond at this time, but marginal relays 41, 42 and line relay 43 of the test distributor E, Fig. 2, pull up, the line relay 143 completing the usual circuit for a slowacting release relay 44. The test clerk's impulse transmitter S is then brought into the control circuit by movement of a key K to the left, and the transmission of the first two digits of the wanted number first raises and then rotates the wipers of the switch E in known manner, to engage the trunk leading to the test selector F, Fig. 3 (assuming that the line to be tested is a party line), capable of extending the test circuit to a test connector H having access to the wanted line. Busy test, busy signal and hold-up if test selector F, Fig. 3, is engaged. In this case the busy relay 48 is energized over test wiper 90 and a busy tone is sent from the machine B to the test clerk. A reversing relay 40 is also energized over armature 78 and reverses the direction of the current through the left-hand winding of the polarized relay 7, which now responds and lights a busy lamp L<1>. The clerk may then disconnect his set by restoring the key K and attend to other duties, the connection meanwhile being held by the bridge across conductors 34, 35. When the wanted trunk to the test selector F falls idle, the busy relay 48 de-energizes, disconnecting the reversing relay 40 and thereby extinguishing the busy lamp L', and energizing the switching relay 49, which locks up ever armature 51, energizes the release relay 115 of switch F over armature 84, and extends the impulse circuit from armature 60 of the line relav 43 to the lead 103. Test selector F, Fig. 3. On noting that the lamp L<1> has extinguished, the test clerk again inserts his impulse transmitter S and sends the third digit of the wanted number, which causes interruptions in the circuit of the line relay 43. Each time the armature 60 relapses the rotary magnet 119 of the selector F is energized in a circuit 70, 63, 77, 89, 103, 117, and the wipers 132 - - 136 are stepped round until the trunk leading to the wanted test connector H is engaged. During the transmission of these impulses the slow-release relays 46, 47 are energized, the former maintaining the release relay 115 energized over armature 73, and the latter opening the test trunks 32, 33 at armatures 85, 86. Relay 117, energized in series with the rotary magnet 119, closes a circuit for the busy relay 118 and prepares an alternative circuit 103, 123, 124 for the rotary magnet 119, which circuit is completed when the relay 116 energizes in series with the release magnet 120 over the off-normal contacts 122. The release magnet 120 does not respond in this circuit. If the test connector H is idle, on the relapse of the series relay 117, the busy relay 118 de-energizes, extending the test conductors 101, 106 to the connector H, and the impulse circuit to the wiper 133. If, however, the connector H is engaged, the busy relav 118 remains energized, and on the relapse of relay 117, the busy relay 48 of the distributor E, Fig. 2, is energized in series with the resistance R<3>, Fig. 3, and completes a circuit for the reyersing relav 40, which lights the test clerk's busy lamp L<1> and gives an audible busy signal as described in the previous paragraph. The resistances of the lower winding of the busy relay 48 and of the resistance R<3> are so proportioned that the potential on the multiples of the test contact 96 is sufficiently near earth potential to mark the selector F busy. The test clerk on noting the busv signals may either release the connection by restoring the key K<3>, or he mav wait for the test connector H to become idle. When this occurs the busy relav 118 relapses, the conductors 101, 106 are extended to the connector H as described above, and the circuit of the busy relay 48 of the distributor E is disconnected at armature 130, thereby extinguishing the test clerk's busy lamp L<1>. Test connector H, Fig. 3. The test clerk now sends the last two digits of the wanted number, operating the line relay 43 as before, and closing the already indicated impulse circuit to the connector H, which is operated in known manner to engage the wanted line. H the called line is busy on the relapse of the slow-release relay 46, Fig. 2, the reversing relay 40 is energized in a circuit 167, 102, 81, 74, 71, and on the relapse of slow release relay 47 an instant later, is held over armature 55. The busy lamp L<1> is now illuminated as before, and the clerk may either listen in by operating key K<4>, or wait for the line to fall idle. When this occurs the lamp L<1> is cut out, and the switching relay 180 of the line-switch C is energized from earth at armature 58, Fig. 2, and operating half-way, disconnects the wipers of the line-switch. Operation if called line is not a party line. In this case the wanted number has only four digits, and the trunk engaged by the distributor E, Fig. 2, leads direct to a test connector, such as H, Fig. 3, having a test conductor 148 terminating in a test contact (similar to contact 96) in the bank of the distributor E. Testing of called line. The test clerk cuts out the dial S by restoring the key K, takes a reading of the testing voltmeter V, which is in series with the testing conductors 30, 31, and makes anv other desired tests. Hold-up of test connection whilst an apparatus man at the called substation makes repairs. The test clerk first rings the apparatus man at substation A by operation of key K<5> to the left, and then by actuating key K<4> places his head-set across the test conductors 30, 31. By moving key K<5> to the right, talking current is supplied to the apparatus man over impedance coils 37, 38 and the two may converse. If the apparatus man has not finished his repairs, the test clerk may hold the connection by actuating a holding key K<2>, which earths the test wire 36 to mark the trunk 32, 33 busy, prepares a circuit for a supervisory lamp L, and energizes a switching relay 20 which (l) disconnects the trunk conductors 32, 33 from the test circuit and bridges across them a relay 16, and (2) holds the connection by bridging the conductors 34, 35 at armature 22. The test clerk :nay now restore the exchange key K<3> and attend to other business. When the apparatus man his finished his repairs he removes the receiver at substation A, thereby energizing the relay 16 and lighting the supervisory lamp L. The test clerk now re-operates keys K<3>, K<4>, and K<5>, and restores key K<2>, thus again connecting his head-set to the called line A. Testing of the line switch C associated with the called line. The test clerk restores the k