209,397. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Compagnie Franþaise pour l'Exploitation des ProcÚdÚs Thomson-Houston). Jan. 8, 1923, [Convention date]. Automatic and semi-automatic exchange systems.-Exchange attendants' apparatus for testing the correct operation of the selectors comprises a number of testing switches adapted to connect the selectors in turn to auxiliary controlling apparatus and alarm arrangements. The controlling apparatus transmits impulses to cause the selector under test to seize either directly or over subsequent selectors a special test line which controls the selector to perform a cycle of operations similar to those performed in the case of an ordinary call. If the selector functions properly a relay energized on the controlling equipment releases the selector and advances the testing switch to the next idle selector. This relay also releases a dash-pot relay, energized at the beginning of the test, before it has had time to close its contacts and cause an alarm to be given. When the first testing switch has tested all the selectors wired to it, a second testing switch is automatically set in action to test a further series of selectors, and so on. Testing connectors. When key C is moved to the right, interrupter I is started over wire M, dash pot relay 21 is energized over contact 41 and relay 15 is energized from ground at 53. Relay 15 energizes relay 16 in series with the stepping magnet 24 of switch C<3> which is not operated at this stage. Relay 16 releases relay 15 and energizes relay 108 of the connector, Fig. 4, connected to the first terminals of the switch C<3>, in a circuit 108, 74, 51, 36, 39, 55 (and 57 in parallel) 53, 75. Relay 108 energizes relay 109 which grounds the release wire 156 to lock up relay 16. Relay 15 on falling back completes a circuit for interrupter I and relay 17 which operates intermittently and sends impulses to the stepping magnet 63 of a sending switch C<2>, Fig. 2. At the first step of switch C<2> relay 18 pulls up owing to the ground on wiper 66 so that subsequent energizations of relay 17 interrupt the circuit of the connector line relay 108. Relay 18 energizes the stepping magnet 64 of the digit switch C<1>. It is assumed that the special test line corresponds to the tens and units digits 2, 0 so that the impulse sending- equipment sends first 2 and then 10 impulses, the number sent being controlled by the cross connections on the frame DI. After 3 impulses by relay 17 (two of which have been received by relay 108) wiper 67 is on the contact grounded by jumper X and relay 19 pulls up and disconnects relay 17 so that relay 108 remains energized. Relay 19 locks up under control of relay 18 and completes a self interrupting circuit for magnet 63 which restores the switch C<2> to the position shown, in which relay 18 is released and releases relay 19. When relay 19 energized it released magnet 64 so that switch C' advanced one.step. On the relapse of relay 19 a further train of impulses is sent out in a similar manner but in this case switch C<2> moves 11 steps before wiper 67 finds ground for energizing relay 19. 10 impulses therefore go to relay 108. Stepping magnet 64 is energized as before and when released by relay 19 moves switch C' a further step. In this position a circuit is made over jumper Y for relay 14 which locks up to the release wire 156 and grounds the bank terminals of wiper 68 to complete a restoring circuit for switch C<1>. Relay 14 also breaks the circuit of relay 17 and removes a short circuit from the upper winding and energizes the lower winding of polarized relay 13, which does not operate at this stage. The connector wipers are now on the terminals of the test line, Fig. 5. Relay 112 energizes in series with relay 120 and sends out ringing current over relay 110. Relay 121, energized by the ring, locks up and connects relay 122 to a very slow interrupter. Relay 122 on energizing cuts the line through to the upper winding of magnet 123, ringing cut off relay 110 energizes in this circuit and relay 107 pulls up and reverses the current in the calling line to operate relay 13. Relay 13 puts the alternating current relay 12 across the line which is being fed with current induced in the upper winding of 123. Relay 12 energizes relay 10 which looks up, energizes magnet 24, releases relay 21, and releases the connector by opening the talking loop. Relapse of relay 109 releases relays 16, 14, 13, 10 and relay 15 is again energized over the key C. Relay 10 on relapsing releases magnet 24 which steps the switch C<3> on to the next set of terminals. If these are busy, ground on wiper 82 causes the switch to move another step. The next idle connector is tested as before. If a connector is faulty relay 10 will not interrupt the circuit of relay 21 and the latter energizes an alarm bell S and lamp L<1>. When the switch C<3> reaches its last terminals contact 80 closes and energizes relay 23, and on the energization of relay 10 at the end of the test, magnet 24 is energized in series with a winding of relay 22 from ground at 41. Relay 22 locks up to ground at 29<1> and cuts through the connections to switch C<4>. Relay 10 on relapsing releases magnet 24 which moves the switch C<3> into its first position, so that contact 80 opens and releases relay 23. If the last connector accessible to C<3> had been busy, magnet 24 and relay 22 would have been energized in parallel from ground on the test wiper over contacts 49, 52, and interrupter contact 81. Switch C<4> now connects its connectors in turn to the controlling apparatus and then switches over to the next switch. When the last connector associated with the last switch Cp, has been tested relay 25 energizes relay 20, Fig. 1, in a circuit 98, 90, 49, 52, 91, to light lamp L<2> and sound alarm S and indicate the end of the test. Testing group selectors. Group selectors may be tested either by having a special test line associated with one of their levels or by causing them to seize over further selectors an equipment such as that shown in Fig. 5. Preferably a separate impulse sending equipment is provided for each class of selector, but alternatively the same one may be used, a relay being provided to change over the connections on the frame DI when a change is made in the class of selector being tested. In the example shown it is assumed that a group selector, Fig. 6, has been taken into use directly by the switch C<3>. Relay 130 energizes over the loop in the same way as relay 108 in the connector and energizes relay 131 to ground the release wire and lock up relay 16. The impulse sending mechanism in this case sends one or two digits according to the type of apparatus so that the wipers 140 - - 142 are stepped to the test line, whereupon relays 129, 133 energize in series over the contact X. Relay 129 extends the talking wires to relay 149, Fig. 7, which grounds terminal 143 over the lower winding of relay 148 to lock up relay 129. Relay 148 locks up and reverses the current in the loop to operate relay 13. Relay 13 switches in relay 12 which operates in response to alternating current sent out over the lower winding of relay 149 and energizes relay 10 as in the case of the connector. The resistance R<1>, Fig. 1 represents the maximum allowable insulation leakage in a line and is permanently connected by relay 16 across the talking loop. The resistance R represents the maximum allowable resistance in a line and is included in the loop when key C is moved to the left. The switches C<3> - - Cp may be Strowger switches.