257,606. Metropolitan-Vickers Electrical Co., Ltd., (Assianees of White, T. U.). Aug. 28, 1925, [Convention date]. Selective distant-control systems; tell-tale apparatus.-In a. supervisory control system for apparatus units or a substation of the kind having chains of counting relays M, M<1> at the control station and substation which are operated synchronously upon the change of condition of an apparatus unit at the substation, or the operation of a key at the control office, to select corresponding supervisory signals or prepare the operating circuit of a unit respectively, and wherein groups of selecting relays N, N<1> at each station, associated with the keys and apparatus units respectively, are connected successively by switching relays 315, 316 and 522, 523 individual to each group to the counting chains M, M<1>, the switching relays at each station are controlled by relays 203, 205, 806, 808 respectively, which are operated from the distant station so as to ensure that corresponding selecting relay groups are operated simultaneously. A complete cycle of operation of the counting chains operates successively the relays of the first selecting groups at each station and then the chains are reoperated to actuate the next selecting relay groups and so on. Figs. 1 to 4 show the control office apparatus and Figs. 5 to 8 the apparatus at the substation. When it is desired to operate any particular unit such as the circuit breaker C, Fig. 5, the corresponding key K<2> at the control office is operated to prepare the operating circuit of the unit and a " start " key K, Fig. 4, is operated to initiate the operation of the relay chains. The selecting relays are energized synchronously in sequence until the relays corresponding to the unit and key are operated when a. circuit is completed over a line 363 for operating the unit. A key K which is common to all the selecting keys at the control station must be depressed to complete the operating circuit. When the unit is operated a circuit is established over the line 364 and the appropriate supervisory signalling lamp such as 328 or 329 is operated. The receipt of the supervisory signal restarts the operation of the relay chains and if the unit is selected by a relav in the first group, the remaining relays in this group and the relays :n the subsequent groups are then operated until finally the apparatus is restored to normal. Each selecting relay at the control office has a key which when operated holds up the selecting operation to enable the operator to remain in connection with a selected unit. Each switching relay at the control station is controlled by a relay such as 203 which is operated from the substation, the switch relays at the substation being suitably controlled from the control office. The counting relay chains are operated synchronously by pairs of control relays 416, 615 and 419, 612 which are alternately connected to the line 470. Normal condition of the system. Normally the relays 406, Fig. 4, and 603, Fig. 6, are energized in series over the line 363. The relay 406 energizes a relay 402 which prepares the circuit of a relay 409 controlling a contact in the line 470. In the event of battery failure at the control office the relay 402 is de-energized and the operation of the selecting apparatus is rendered impossible. A relay 610 at the substation is provided for a similar purpose. Selection of circuit breaker C, Fig. 5. Assum. ing it is desired to close the circuit breaker C, the key K<2> is operated into a position opposite to that shown and the " start " key K is depressed and released to bring about the energization of the relays 404, 405 which open the holding circuit over the relays 406, 603. When the relay 406 is de-energized, a relay 409 prepares the circuit over the line 470. De-energization of the relay 603 at the substation operates relay 601, which completes the line circuit and energizes the line relays 416, 615. The relay 416 operates a relay 413 which energizes the first counting relay 113 and a relay 411. The relay 411 de-energizes a normally energized relay 401 which operates a relay 408 to open the line circuit. The counting relay 113 completes the circuit of the next counting relav 112 which however remains inoperative due to a short circuit produced by the original energizing circuit of the relay 113. When, however, the line circuit is opened, this short-circuit is removed and the relay 112 is energized to prepare the circuit of the counting relay 125 and operate the relay 317. De-energization of the line relay 416 also causes the operation of the relav 420 which transfers the line 470 to the relav 419 at the control office. The relay 317 energizes a relay 319 which opens the circuit of a relay 407 to de-energize the relay 408 to again prepare the line circuit. At the substation the line relay 615 operates the counting relay 712 which causes the energization of the next counting relay 713 when the line circuit is opened. The relay 713 operates a relay 518 and prepares the circuit of the next counting relay 700. The relay 518 operates a relay 611, the circuit of which is prepared by the relay 602 when the line relay 615 is de-energized, to transfer the line circuit to the relav 612. The relav 602 also transfers the line circuit which is thus completed over the relays 419, 612. The relay 419 operates the next counting relay 125 which opens the short-circuit across the relays 318, the circuit of which is prepared by the relay 317. The relay 318 connects the apparatus unit control and supervisory lines 363, 364 to the contacts of the selecting relays. The relay 612 at the substation similarly operates the next counting relay 700 which causes the relay 520 to connect the lines 363, 364 to the selecting relays at the substation. When the line relay 419 is energized, the relay 408 is operated to open the line circuit and the relay 420 is de-energized to again establish connection with the line relay 416. Similarly at the substation the line is transferred to the relay 615 in readiness for the next impulse. When the line circuit is opened the next counting relays 124, 701 at each station are energized to operate the first switching relays 315, 523 and in consequence, the first selecting relays 314, 507. Operation of circuit breaker. These relays. which are associated with the operated key, complete an operating circuit over the contacts of the keys K<1>, K<2>, relay 314, line 363, contacts of relay 507 to a relay 503. The relay 503 energizes the coil 505 which closes the circuit breaker C. Signalling condition of circuit breaker. On closing, the circuit breaker opens the circuit of relays 502, 501. The relay 501 de-energizes the relay 500 which completes a signalling circuit over the contacts of the relay 507, line 364, contacts of relay 314 to a relay 303 which illuminates the lamp 328 and extinguishes the lamp 329. A relay 304 also operates a relay 301 and thereby energizes the relay 319. The relay 319 causes the de-energization of the. relay 408 and the line circuit is again completed over the relays 416, 615. Completing the cycle of operations. The remaining selecting relays at each station are then operated under the control of the counting relay chains. If no further apparatus unit controlling operation is desired, the selecting relays are operated without hesitation since after the operation of each relay, the relay 319 is operated over the contacts of the selecting key, which is in a position corresponding to the position of the associated apparatus unit, and the circuit over the line 470 is closed to transmit the next impulse. When finally the counting relays 115, 710 are operated the selecting relays 305, 516 and the switching relays 315, 523 are de-energized. De-energization of the relav 305 opens the circuit of the relay 319 which by means of the relays 407, 408 opens the line circuit. When the line circuit is opened the next counting relays 114, 711 are operated to energize relays 201, 800. The relay 201 closes a circuit over the lead 18, line 364 to relay 806 at the substation which in turn establishes a circuit over the lead 581, line 363, to relay 205 at the control office prepares a circuit for the corresponding switching relay 316 and also completes the line circuit to operate the next counting relays 101, 724. These relays open the circuits of the relays 205, 806 and also the line circuit to allow the next counting relays 100, 725 to release the operated counting relays, disconnect the lines 363, 364 from the selecting relays and complete the holding circuit over the relays 405, 603. When as previously described the switching relay 315 is operated a relay 209 is energized to prepare the circuit of the relay 404 over the lead 231. The locking circuit of the relay 404 is opened at the end of the operation of the first group of selecting relays, but the relay is again operated over its prepared circuit to again open the holding circuit over the relays 406, 603. The holding circuit is also opened automatically at the substation by a relay 606 and the cycle of operations is again initiated. When during the second cycle of the counting relay chains, the relays 124. 701 are energized, the switching relays 316, 522 are operated since their circuits are, as previously described, prepared by the relays 205, 806. The selecting relays in the second groups are then operated successively to connect the apparatus units associated with these groups to the line wires. 363,364. When the counting relays 114, 711 are energized, the controlling relays 203, 808 are operated to prepare the circuits of the switching relays 315, 523 in readiness for the next operation after the equipment has restored to normal. The operation of the remaining relays in the counting chains restores the apparatus to normal, reoperation of the relay chains now being impossible since no ,circuit is prepared for the rel