360,515. Electric distant control and signalling systems. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Oliver, J. H. ; 7350, Buist Avenue, Philadelphia, U.S.A.) Aug. 15, 1930, No. 24512. Convention date, Aug. 16, 1929. [Class 40 (i).] In a supervisory control system for apparatus located at a remote station, selection of a particular apparatus is checked and the position of such apparatus is signalled prior to its operation. The checking signal constitutes a code of impulses which operate an audible signalling device, and the pitch of the impulses is determined according to the position of the selected apparatus. The system also facilitates the control and supervision of apparatus having a plurality of positions e.g. field rheostats, water gates, &c. Fig. 1 shows the apparatus at the control office A connected by line wires L to part of the selective equipment of the remote station, the remainder of which is shown in Figs. 2 and 3. Any one of the apparatus units 1 .. 5 may be selected by a characteristic code comprising three trains of impulses, transmitted by the impulse sender 20, Fig. 1. When selection is accomplished a switch 5S, Fig. 3, is operated to mask a code sending switch 6S in a manner characteristic of the selection. The switch 6S transmits impulse trains to operate an audible receiver 17, the pitch of the signals being determined by buzzers 12, 13, Fig. 1, according to the position of the selected unit. For signalling the position of apparatus such as 4, 5, Fig. 3, a number of impulses characteristic of the position is transmitted by the switch 6S which is marked by a chain of relays 140 .. 149 associated with the apparatus 4, 5. Selection of apparatus unit. To effect a particular selection three trains of high-frequency impulses are transmitted by operation of the dial sender 20 the contacts 23 of which interrupt the primary winding of an induction coil the secondary of which is connected across the lines L. The impulses operate a relay 27 connected across a filter F, F<1> adapted to prevent the flow of low-frequency current, and causes energization of relay 29 to close circuit of the stepping magnet 31 of switch IS over wiper of switch TS. The switch 1S is thus operated according to the first impulse train at the termination of which relay 32 is released to operate magnet 33 and step the transfer switch TS into its first position to transfer the impulsing circuit from switch 1S to switch 2S. The second train is thus recorded upon the switch 2S and the third train upon switch 3S. At the end of the third train switch TS is again operated. In this manner the switches 1S, 2S, 3S occupy positions characteristic of the transmitted signal and a circuit is closed over the switches and switch TS to select a relay e.g. 39 to shortcircuit a corresponding relay e.g. 211 associated with the selected unit. The relays 1<11> . . 5<11> associated with the various units are normally held energized over contacts controlled by the units. Checking signal. When relay e.g. 211 is released, potential is removed from corresponding contact of switch 5S and relay 46 is energized to initiate operation of switch 5S which automatically steps up to the marked contact. In this position the switch marks the code transmitting switch 6S in a manner characteristic of the selection effected. A relay 47, controlled by relay 46 but which remains short - circuited during stepping of switch 5S, now pulls up and energizes relay 68 over wiper 6S-4 of switch 6S. Relay 68 operates relay 69 which energizes magnet 66 to step switch 6S and deenergize relays 68, 69 and magnet 66 and thereby effect repetition of the cycle of operations. The switch 6S is thus stepped continuously to transmit repeated code signals corresponding to the marking effected by switch 5S, a relay 14 being energized or de-energized according to the position of the selected apparatus to select one or other of the buzzers 12, 13 which transmit signalling current to line. The buzzer circuit is interrupted at each step of the switch 6S the particular code of impulses sent being determined by relay 73 which operates over the marked contacts of the switch 6S to open the buzzer circuit at the appropriate points in the cycle and thus transmit a corresponding code of three impulse trains. Operation of selected apparatus. In order to operate a selected apparatus one or other of two impulse trains is dialled to operate switch 4S into corresponding position and operate one or other of the relays 19, 19<1>. This relay closes the circuit of the actuating magnet of the selected unit over wiper 3S-4. When the unit changes position the relay 14 is reversely affected to alter the pitch of the checking signal and thus notify the control office that the operation is correctly performed. The relay 19, 19<1> operates relay 100 which effects self-drive of switch TS to normal. The selected unit may be operated as often as desired, the selective connection being maintained independently of the operating signals. In the event that an impulse code, other than a correct code for operating a selected unit is transmitted relay 88 is energized over switch 4S and the equipment is restored to normal. Restoration of selective equipment. Restoration is effected by key 18, Fig. 1, which when operated transmits a d.c. impulse to operate relay 110. Relay 110 operates relay 50, 90 which effect the restoration of all the selecting, marking and code transmitting switches. Checking condition of remote equipment and line wires. If when the system is in normal condition it is desired to check condition of the equipment or line wires, the key 18 is depressed and relays 110, 50 are energized to operate low pitch buzzer 13 over the contacts of normally energized relays 118, 120. Signalling automatic operation of apparatus units. When an apparatus unit changes position automatically the associated relay e.g. 2<11> is de-energized to remove normal potential on corresponding contact in bank of switch 5S. Relay 46 also is operated to initiate stepping of switch 5S up to the marked contact and energize relay 47 to cause switch 6S to send the appropriate code signal. The signal is interrupted by operation of the reset key 18 which, if one unit only is operated, restores the switches to normal. If however several units have changed position operation of the key effects stepping of switch 5S on to contacts corresponding to the next unit to re-mark switch 6S and effect transmission of the appropriate signal. This operation is repeated for all units which have changed positions automatically. Signalling and controlling position of units having more than two positions. In order to ascertain the position of a unit e.g. 4, the associated relay 411 is de-energized in response to a code signal from the control office. Relay 4<11> causes operation of a relay in the chain 140 .. 149 characteristic of the position of the unit which relay appropriately marks switch 6S. Relay 46 also effects operation of switch 5S up to a marked contact and relay 47 initiates operation of switch 6S to transmit im. pulses, the number of which is indicative of the position of the unit. The position of the unit may be altered by transmission of one or other of two impulse trains to operate a polarized relay in one or other direction. The relay effects control in one or other directions of motor mechanism for driving the unit. Telephonic communication. Normally telephone apparatus t, t<1> are associated with the line wires but the apparatus at the control office is disconnected upon actuation of the key 18.