Patent GB-291384-A (GB)
Title: Improvements in and relating to remote electric control systems
IPC: H02J13/00
Filed: 1928-05-31
Abstract: 291,384. British Thomson-Houston Co., Ltd., (Assignees of Allen, H. E.). May 31, 1927, [Convention date]. Selective distant control systems.-In a system of selective distant control by means of carrier currents over a system of distribution comprising a plurality of feeders means are provided selectively to connect the transmitter to the feeders and for keying the transmitter and to disconnect the transmitter from the feeder. Fig. 1 shows a keying switch 47 for a thermionic generator 1 energised from an alternating source through a switch 10 and adapted to be connected to feeders A, B. C. through switches 20, 21, 22. Control devices 24, 25 are hand actuated and, as shown, close and open remote switches. The devices 24, 25 control the switches 10, 47 to render operative and key the transmitter 1 and plug and jack switches 36, 37, 38 provided with a bridging member 40, Fig. 2, effect the selection. Indicating devices 26, 27, 28 are associated with each feeder and operation. To open a switch on feeder A a plug is inserted in the corresponding jack 36 and the appropriate control device 25 is operated. Fig. 3 shows the construction of the control device comprising a handle 77 and operating member 76 adapted to be rotated in a clockwise direction through 360‹ and close contacts 57<1>, 64<1> and contacts 61', 66<1> to operate relay 10 and relay 43 respectively, thus energising the transmitter and operating the indicator 26 which is selected by the jack 36. The return of the shaft 73 causes rotation of a shaft 74 through discs 78, 79 and pawl 81 carrying coding devices 80, having contacts 51', 52<1>, 53<1> associated with lines 51, 52, 53. Line 51 is selected by the switch 36 so that a signal corresponding to the code disc is sent through the keying switch 47 on the feeder A. The return to normal of the control device deenergises the transmitter by opening contacts 57<1>, 64<1>. At the remote station, Fig. 6, a thermionic valve 92 detects the signal and operates relay 100 controlling an induction relay which controls the circuit breaker 116. In a modification (Fig. 4 not shown), in which two different sets of switches are operated on one of the feeders an additional plug and jack selecting device and an additional indicating device is employed. When all the feeders are operated in response to the same code (Fig. 5 not shown), the centre contacts of the selecting devices 36, 37, 38 are parallel connected. Provision for manual control independent of the control devices 24, 25 is provided by switch 142 which controls switches 10, 47 and the selecting switch 20, 21 or 22 selected by the plug and socket selecting devices 36, 37, 38. Keying may be effected by a handoperated switch in conductor 46. Fig. 7 shows the construction of the induction relay, which comprises a coil 117 rotating through gearing a disc 119 to drive members 122, 135 operating a mercury tube 123. The receipt of a short :rnpulse causes the member 122 to engage a member 134, which operates the member 131, which rocks the tube 123. A long impulse causes member 135 to engage a member 132 to rock the tube 123 in the opposite direction. Members 122, 135 are spring returned, and member 122 on its return is inoperative as the member 13-1 is freely mounted on the shaft. The detecting valve 92, Fig. 6, is energized through transformer 97, the grid bias being obtained from a winding 103 so arranged that a negative bias is applied while the valve is operative. To maintain a 180‹ phase relation between the voltages applied to the grid and plate a resistance 104 is provided to compensate for the phase displacement caused by other apparatus associated with the grid and plate circuits. The transmitter 1, Fig. 1, comprises a pair of parallel connected valves 2 associated with a tuned circuit 14 and energized through transformer 5. The output transformer 16 is preferably of the high impedance type, so that variations in the impedance, of the feeders does not affect tuning, and the secondary is preferably tapped to match the impedance of the feeder to that of the transmitter. The receiver transformer 106, Fig. 6, is similarly of the high impedance type and resonant to the frequency employed, and is so constructed as to reduce reflection losses and to diminish the effect of the apparatus on the carrier energy lead of the feeder.