Patent GB-308967-A (GB)
Title: Improvements in or relating to electric remote control systems
IPC: B61L7/08
Filed: 1929-02-28
Abstract: 308,967. Associated Telephone &. Telegraph Co., (Assignees of Nelson, M. L.). April 2, 1928, [Convention date]. Selective distant control systems; order and tell-tale apparatus.-In a system for selectively controlling lamps, semaphores, circuit breakers &c. at stations located at a plurality of points along a common trunk line from a central station, selection is checked at the central station by an audible code signal and the position or condition of the apparatus at the selected station is indicated by the tone of the audible signal. The Figure shows two substations A, B adapted to be selectively controlled from a control station D, the apparatus at station A being shown in detail. Each station is selected by a characteristic impulse code transmitted by the impulse sender 30 at the central station. The code operates two-dimensional selecting switches at all stations, but apparatus such as the lamps 79, 80 is associated, with the trunk line through the switches only at the appropriate substation. An audible signal characteristic of the selected station is transmitted back to the control station by a code disc, such as 68<1>, the tone of the signal being determined by low or high pitch buzzers 25, 26 according to the condition of the signal lamps. The apparatus, e.g. one or other of the lamps 79, 80 depending upon which is inoperative at the selected station may then be operated by the transmission of further impulses, and the initial condition of the apparatus may then be re-established by another train of impulses so that alternate operation of the apparatus may be effected by successive trains of impulses. Indication of the condition of the apparatus is reverted continuously during the selective operations. Selecting substation. Assuming it is desired to select station A, the telephone, receiver R at the control station is lifted to energize the line relays 1, 27, &c. at all stations. These relays energize slow-release relays such as 2, to prepare the circuit of the stepping magnets of the selectors. The impulse sender is then operated to transmit the code characteristic of the station A, the first train of impulses operating the vertical stepping magnet 14 and the second train the. horizontal stepping magnet 16 to position the wipers 55, 56 upon the appropriate, contacts. At all other stations the switch wipers are positioned upon " dead " contacts. A slow-release relay 4 also is operated in parallel with the magnet 6 to prepare the circuit of relay 5 which energizes in series with relay 6 upon cessation of impulsing to prepate the operating circuit of the lamps 79, 80 over wiper 55 at the station A. Checking selection. Operation of relay 5 energizes a relay 24 over wiper 56 to operate one or other of the buzzers 25. 26 in series with the primary winding 82 of a transformer the secondary winding 81 of which is connected in an answer-back signalling circuit. Operation of relay 24 also causes a repeated cyclic operation of relays 22, 20, 18 to impulse a magnet 17 for operating a coda disc 68<1> step-by-step to transmit the audible code characteristic of the selected station. The checking signal is repeated continuously throughout the selecting operation. A disc 69<1> is provided to ensure the return to normal of the code disc 68' in the event of abandon. ment of the call prior to the disc 68<1> reaching its normal position. Operation of apparatus at selected station. In order to operate the lamp 79, a further train of impulses is dialled to operate relay 4 and thereby cause energization, upon cessation of impulsing, of relay 7 and the operation of locking relay 10 over wiper 55. Relay 10 operates locking relay 12 which reverses the indication of lamps 79, 80. A relay 9 is energized in series with lamp 79, to prepare the alternative operating circuit of lamp 80. A further train of impulses then causes operation of locking relay 11 to energize relay 13 to cause release of relay 12 and reoperation of lamp 80. In this manner the lamps 79, 80 are alternately operated in response to successive trains of impulses while the apparatus remains in its selecting position. Signalling operation of apparatus. Relay 9, which is energized or not according to whether lamp 79 or 80 is operated controls a contact 58 which connects either the low pitch or high pitch buzzers in the answer-back code signalling circuit. Release. In order to restore the equipment to normal condition the receiver R is replaced to cause de-energization of the line relays 1, 27, &c. and the consequential operation of the release magnets, such as 15, of the stepping switches in all stations.