Patent GB-669420-A (GB)
Title: Test boards for telephone systems
IPC: H04M3/22
Filed: 1949-05-23
Abstract: 669,420. Automatic exchange systems. DEHN, S. G. (Automatic Electric Laboratories, Inc.). May 23, 1949, No. 13723/49. ,Class 40 (iv). I The speed of impulsing of a transmitter such as a dial is tested by counting the impulses on a first chain of relays while impulses from a standard generator are counted on a second chain of relays, the second chain being stopped under the control of the first to control further apparatus to show whether the speed is fast, standard or slow. Several other tests are described including one for giving the length of each impulse. To facilitate reference to the Specification, the same section headings are used in the Abridgment. The invention is concerned with a test-board 200 having access to several circuits, shown schematically in Fig. 1, including subscribers' substations. The detailed circuits are set out in Figs. 2-21, arranged together as shown in Fig. 22. The test-board is of multi-position type and' comprises several common and special test keys, those keys indicated by F and R being paired to permit operation of only one of the pair. Local calls by a subscriber are effected in known manner by dialling four digits. Section 4. Ordinary calls from a subscriber to the test-board. A subscriber at T, Fig. 4, dials four predetermined digits and in known manner causes a connector 415 to select a trunk 510 to a ring-down trunk circuit 500, operating ring relay R525 which momentarily releases hold relay R530 and lights answer lamp L514 on the test-board 200. The attendant actuates the associated ring-down key K545 which causes connector 415 to switch through to the subscriber and restore the ring relay. Key K545 also operates answer relay R540, which re-operates hold relay R530, after which R540 restores slowly and the connection between the trunk 510 and the test-board is complete. Operation of first test key K231R connects line conductors C402, C403 to test conductors C271, C272 and insertion of plugs P813, P815 into jacks J814, J816 permits conversation between attendant and subscriber over talk repeater 821. Plug P813 closes contacts 817 to connect test battery 1525 to the test circuit and light test battery lamp L1516. Power relay R1595, however, is also energized to operate power check relay R1590, which, if the A.C. power supply is in order, replaces the battery by power rectifier 1524 and extinguishes lamp L1516. The attendant then tests the subscriber's line in various ways described later and restores keys K231R and K545 to release the circuit. Section 5. Inspector calls from a subscriber line to the test-board. The inspector seizes the subscriber line and dials predetermined first and second digits to cause the first selector, say 413, to select an idle special second selector, say 416, and an idle incoming trunk, say 490, incoming to a trunk circuit 400, so operating line relay R440 which returns ring-back tone current, operates hold relay R435 to mark the trunk 490 busy and lights answer lamp L445 to indicate that an inspector trunk 210 is calling. The attendant depresses the related talk key K485F to operate switch relay R460, so extinguishing the answer lamp and connecting the subscriber line over trunk 490 and inspector trunk 210 and talk repeater 821 to the test-board attendant. Operation of key K485F also causes tone relays R470, R475 to return a short splash of dial tone to the inspector. The attendant may now make certain tests, described later, by operating the related test hold key K485R, restoration of which breaks the connection to the inspector trunk. Section 6. Direct calls by a test man from a subscriber substation to the testing apparatus at the test-board. A test man at the subscriber substation by dialling a special digit may obtain access to the testing apparatus over trunk 495 without the aid of the attendant. By dialling, the test man causes the operation of line relay R1100, which energizes pulse relay R1280 and so hold relay R1230, which applies ground to control conductor C498 to hold operated the special second selector 416 and mark the trunk 495 busy. Hold relay R1230 also lights busy lamp L1210 to indicate to the attendant that the testing apparatus has been seized by the test man, who now dials certain digits to control line relay R1100 to perform certain tests described later. Release by the test man restores all associated apparatus. Section 7. Calls from the manual switchboard to the test-board. When the manual operator wishes to test a circuit, she speaks to the test-board attendant who assigns a test trunk, say 575, to the manual operator and actuates test-trunk key K580 and second test key K232R. Section 8. Ordinary calls from the testboard to a subscriber substation. The attendant may use dial trunk circuit 600 by operating out-dial key K615 and second test key K232R to energize the left-hand winding of answer relay R610 which thus becomes polarized. Battery is also provided through the winding of dial relay R620 to the dial conductor C277, and the conductors of trunk 605 are connected to test conductors C271, C272. Key K615 also bridges the right-hand winding of answer relay R610 across the conductors of trunk 605 but as R610 is polarized it does not pull up. Line circuit 417 grounds the associated start conductor C609 to operate distributor 411 and it is assumed that the finder 412 seizes the trunk 605 and returns dial tone to the talk repeater 821. The attendant then uses dial 1428 to operate dial relays R1460, R620, the latter replacing the bridge across the righthand winding of R610 by a direct connection to line conductors C264, C265. R1460 completes an impulsing path through dial 1428 across test conductors C271, C272 and impulses are transmitted to the first selector 413, whereby in known manner the subscriber line is called. When the subscriber answers, connector 415 reverses the polarity, whereupon the right-hand winding operates answer relay R610 to light supervisory lamp L612. Section 9. Calls from the test-board via the line test circuit to a subscriber. Insertion of shoes S365, S366 into jacks J371, J373 and plugs P363, P364 into jacks J361, J362 retains the related subscriber line, say 401, in service although contacts 372, 374 are opened to allow insertion of the line test circuit 300. Operation of listen key K351R connects the subscriber's line conductors C402, C403 to line conductors C254, 255 which are connected by operation of first test key K231R to test conductors C271, C273, whereby the attendant can listen. If he finds the subscriber line idle, he may test the outgoing section comprising line conductors C402, C403 by restoring the listen key and operating out-line key K352F to energize outline relay R320 and in-drop relay R330, so operating out-line slave relay R340, whereby alternative connections, excluding condensers 316, 317, are made from jacks J361, J362 to conductors C254, C255 to enable certain tests to be made. Alternatively, to test the in-drop section, i.e. conductors C404, C405, in-drop key K352R is thrown to energize R330, the marginal out.line relay R320 remaining inert, and conductors C254, C255 are connected to conductors C404, C405, whereby certain tests may be made. At this time, ground on test conductor C271 operates loop hold relay R1440 to energize loop test relay R1445 which bridges R1440 across the windings of retard coil 1434 and so across the windings of line relay R420, which pulls up, dial battery lamp L1417 lighting up. R420 operates the .distributer 411 and the attendant may now extend the connection to another subscriber, afterward restoring the in-drop key to release all apparatus. If in this test, lamp L1417 does not light up, the attendant suspects a high-resistance short circuit between the line conductors C402 C403, whereby insufficient current flows through the upper winding of line relay R420 to operate loop hold relay R1440. He attempts to clear the fault by operating talk battery key K1411 and test reverse key K1510 to reverse potentials on test conductor C271, C272 shunting the windings of R420 through the windings of retard coil 1433, whereby if the short-circuit has high resistance, line relay R420 releases to restore lock-out relay R430. The attendant then restores keys K1510, K1411 to light lamp L1417 as described before. If however, the shortcircuit is of low-resistance type, line relay R420 cannot be restored in this manner and an order is given for repair of the line. To test the heat coils HC381, HC382 the attendant actuates heat coil key K351F and first test key K231R to connect the coils between line conductors C254, C255 and ground on conductors C404, C405, after which the attendant tests the heat coils selectively. Section 10. Calls from test-board via test distributer trunk circuit to subscriber line. Operation of test distributor key K725 and first test key K231R energizes seize relay R710 to seize the test distributor circuit 700, busy lamp L722 lighting up. R710 also operates hold relay R745 and key K725 energizes in series the windings of release relay R780 and battery cut-off relay R770, the latter being marginal and not operating. The keys connect test conductors C271, C272 over line conductors C254, C255 to line relay R2020, which, in a manner similar to that described in Sect. 9, operates in series with loop-hold relay R1440, hold relay R2025 and loop-test relay R1445 also pulling up to light lamp L1417 to show that the circuit 700 has been seized. R2025 operates transfer relays R2030, R2065. Line relay R2020 now responds to impulses from the attendant's dial and is followed by the lower winding of transfer relay R2030 and vertical magnet M2090 to step the wiper carriage of a Strowger switch vertically for the first digit, after which R2030 restores. In the second digit, R2020 is followed by transfer relay R2050 and rotary magnet M2091 to drive the Strowger switch in the rotary direction, R2050 restoring at the end