310,984. Reyrolle & Co., Ltd., A., Leeson, B. H., and King, O. C. F. Dec. 6, 1927. Selective distant control systems and apparatus; tell-tale apparatus.-Relates to a remote control and indicating system in which three line wires are utilized in pairs for the transmission of selective and executive currents from the control station and of indicating currents from the substation and in which a clean metering circuit over a pair of line wires can be established. The lower half of Fig. 1 shows the control station connected by line wires 10 - - 12 in a cable having a lead sheath 13 to the sub-station. Selection of appaiatus :-The operation of the selector push 230 energizes one coil 240 of the stepping magnet which rotates the control station selector 220 a half-step and locks itself and sends an impulse over wires 11, 12 to the sub-station polarized relays 130, 135. Relay 130 energizes selector relay 120 which closes the circuit of the selector stepping magnet 51 of the selector 50, but relay 135 which controls the metering circuit as will be subsequently described, is ineffective as relay 130 is operated. The energization of magnet 51 closes contacts 52, 53 to apply battery 100 or an alternating current source to line wire 10 and lead-sheath 13. At the control station when the push 290 is released this source over lino wire 10 and the lead sheath 13 energizes coil 241 to step selector 220 a second. half step. Selection of the third and later positions is obtained by further operations of the push 230. The construction of the indicator and selector mechanism may be as described and interlocking mechanism may be provided as described in Specifications 307,379, 307,381, 307,383. In a modification the two selectors may be driven by two solenoids connected in series the arrangement being such that the first movement of either solenoid causes, as by short-circuiting a resistance, the current to increase to ensure the proper energization of the other solenoid. Indicating circuit :-During selection the indicating circuit is opened at contacts 244 and on completion of the selection an indicating circuit is closed over line wires 10, 12 for the polarized relay 210 from the indicating bus bars 112, 113. In the first position " off normal " of the selector 50, the bus bars 112, 113 are connected through contacts 27, 28, 73, 74 to the substation battery 100 with polarity depending on the position of the circuit breaker 20. The polarized relay 210 energizes one or other of relays 213, 2114, which control an indicating device and lamps 301, 306. In the third position the indicating bus bars 112, 113 are associated with a thermostatic switch 30 and associated relay 31. Operation of circuit breaker :-Push 260 trips and push 265 conespondingly closes the selected circuit breaker by energizing the line wires 11, 12 to operate relays 130, 135 in the opposite sense to that in which they were energized during selection so that executive relay 140 is actuated and closes a retaining contact 143 and a contact 144 in the circuits of the trip relay 160 and close relay 170. Relay 135 as during indication is ineffective since relay 180 is operated. The circuits of the trip and close relays also include contacts 23, 24 associated with the circuit breaker so that the latter if open is closed by the energization of the appropriate operating coils 21 or 22, relay 160 or 170 being meanwhile locked by contact 163 or 171. Transmission of meter readings : Meter readings may be obtained in all selector positions and after the desired selection a metering relay 135 is operated by metering push 270 through resistance 279 so that the selecting relay 130 which is in series is not operated. The close meters relay 150 and the auxiliary relay 155 are actuated so that metering bus-bars 118, 119 are connected through contact 158 to line wires 10, 12 with which meters 290 - - 292 are associated by contact 277 on the metering push 270. The bus bars 118, 119 are connected through the selector 50 to meter transformers 40, 41, 42 according to the selector position. The return to normal of the metering push 270 which is of the rotary type (Figs. 2 - - 5, not shown) closes contacts 274, 276 to send current of opposite polarity to line wires 11, 12 through resistance 279 so that relay 135 is oppositely energized. Contacts 136 on closing energize the release meters relay 138 to de-energize relay 155 and restore the indicating circuit. In a modification a metering system similar to that described in Specification 307,379 may be employed. Telephone and alarm circuits. These are associated with the zero or normal contacts of the selectors. The telephone push 280 extinguishes lamp 301 and energizes line wires 11, 12 so that executive relay 130 is operated to complete the telephone; buzzer 182 and speaking circuit 180 over the metering circuit 10, 12. Calls from the substation are effected by push 183 which is electromagnetically looked by electromagnet 186 in all, except normal, positions of the selectors. Current interrupted by interrupter 187 is thus sent over line wires 10, 12 to the control station and operates relay 210 to operate relay 213 and, since the alarm relay 250 is energized in the normal position of the selector, lamp 306 and buzzer 305 are operated. An alarm is given by automatic operation of a circuit-breaker or the operation of thermostat 30 causing the alarm relay 190 to be energized momentarily. Relay 190 locks itself until released by operation of the selector and applies current to line wires 10, 12 in opposite direction to that of a telephone call. The operation of relay 210 thus energizes relay 213 or relay 214 to change over lamps 301, 306 and operate the buzzer 305. Relays 213, 214 control separate indicator discs so that a distinguishing indication is given, moreover, in the case of a telephone call interrupter 187 is in circuit so that the buzzer 305 is intermittently operated. Modification of alarm circuit:-To enable an alarm to be given to the control station during the time meter readings are being taken the substation alarm relay 190, Fig. 7, may be provided with extra contacts controlling an auxiliary alarm relay 480 and its retaining circuit includes a time limit relay 490 in addition to selector contacts. With this arrangement an alarm initiated by any change in the substation apparatus during metering breaks the metering circuit and an alarm is transmitted until the time-limit, relay 490 operates when the metering circuit is re-established. At the control station the operation of the meters push has prepared the circuit of an alarm relay 331 which is energized by an alarm and locks itself until released by the operation of push 335. Arrangements for express selection. To obtain express selection after the operation of contacts 231, 233, Fig. 1, if boths sets of contacts are closed the resetting movement of solenoid 241 will automatically re-energize the starting solenoid 240. The arrangement is similar to that described in Specification 307,379 and may be effected by a special push or by the provision of extra contacts 232 on the push 230 which are closed by rotating the push or alternatively by retaining the push depressed. When selfrecording indicating mechanism is employed at the control station the receipt of an alarm signal may be arranged to cause the selectors to perform a complete selecting and indicating cycle. For this purpose the control station relay 250 is energized in the normal position so that an alarm causes relay 214 to energize an ,additional, alarm. relay 310 which locks itself, starts an express selection over a circuit including contacts 215 controlled by the indicating mechanism so that the receipt of the indication starts the next selecting movement. Relay 310 energizes an auxiliary relay 320 which locks itself till released by theoperator at the control station. The operation of the selector to the fourth position releases the alarm relay 310 but the selecting circuit is maintained by contacts of the auxiliary relay 320 in conjunction with contacts operated by cam on the selector so that the cycle is completed. The control operator can check the system by energizing alarm relay 310 by a push 315. Repeater system for metering circuits : Meter readings directly taken over the line wires would be unreliable owing to variations in the line conditions. Fig. 6 shows a system in which current readings are taken when selector contacts 401 or 411 are closed, potential readings are taken when contacts 421 are closed and wattage readings are taken when contacts 431 are closed. In each selected position one of relays 402, 412, 422, 432 is energized and associates the source with current bus bars 442, 443 or 450 - - 452 and voltage bus bars 445, 446 or 453 - - 455, respectively The bus bars control a group of master repeaters 460 one for each type of meter required each having an operating coil or coils 461 controling a pointer 462 carrying contacts 464. The follower element 466 connects through contacts of the operated relay 402 the substation battery to one side or other of the field coil 471 of a common auxiliary motor 470. The motor 470 drives a rheostat arm 472 to control the energization of the follower elements' 466 which are in series with the line wires 10, 12 through the contacts of meter relays 150, 155, Fig. 1. The control station meters 290 - - 292 are selectively connected in the circuit of line wires 10, 12 and comprise ammeter movements appropriately calibrated.