Patent GB-445096-A (GB)
Title: Electric selective receiving apparatus responsive to code signals
IPC: H04L15/26
Filed: 1935-11-22
Abstract: 445,096. Distant - control systems. LITSTROM, A. S., 24, Sibyllegatan, Stockholm. Nov. 22, 1935, No. 32438. Convention date, Nov. 23, 1934. Addition to 400,014, [Group XXXIX]. [Class 40 (i)] The selector described in the parent Specification and utilizing two timing devices, one for checking the minimum length of marks and the other checking in succession the excess length of a mark over the minimum and the maximum space interval, is modified mainly by using a signal responding relay having only one moving contact and a register preparing relay having two windings, one held in dependence on the signal relay and the other on a relay controlled by the second mentioned timing device. The relays operated by the timing devices are energized over grid-controlled valves. The entire equipment, receiver and selector, is energized from a supply circuit V and an alarm is given if a valve filament fails. Operation for correct signals. On receipt of a mark, normally operated signal relay 1 relapses and removes charging potential from the " minimum " timing condenser 15 which discharges for 3 seconds, whereupon the potential on the grid of valve 8 is such that anode current operates relay 2 which is followed by 5 (upper) and 3 (lower). Relay 5, which energizes winding 61 of the step-by-step register 6 to permit stepping pawl coming into action, holds over its upper winding dependent on signal relay 1 and over its lower winding dependent on relay 4 which in case of correct signals is not operated at the same time as 1. Relay 5 therefore holds for the duration of a correct signal. Relay 3 permits the second timing condenser 25 to discharge, but as the mark is assumed below maximum length, the discharge is without effect. When the mark ceases, 1 re-operates, condenser 15 is re-charged, valve 8 is disabled and relay 2 relapses to change over from the lower to the upper winding of relay 3. These windings of 3 are differential so that 3 momentarily releases. The relapse of 2 sends an impulse to register magnet 62, and the momentary relapse of 3 re-charges condenser 25 to start the timing of the interval. After 2 seconds, valve 9 passes sufficient current to operate 4, but the next mark comes in before this occurs so that 5 remains held. When the next mark has persisted for the minimum duration, 2 pulls up as before, the windings of 3 are charged over and the momentary relapse of 3 re-charges 25 to disable valve 9 and release relay 4. The re-charge of 25 commences the timing of the excess period of the second mark over the minimum and the operations described above are repeated until three correct marks correctly spaced are received. After three steps, the register opens contacts 60, 69 which disconnect the filament heating circuit (see later) and release relay 7 which brings in the alarms 100, 101 remaining dark since its circuit is open at 69. Rejection of incorrect signals. If the first mark is too short, the selector is not affected, but if a second or subsequent mark is too short, 1 is operated, 2 is not and 4 is still operated from the preceding interval timing operation so that both circuits of 5 are open and the register is released, relays 3 and 4 also releasing. If a mark is too long, 4 pulls up when the excess period of 2 seconds has elapsed (length of mark over 5 seconds) and opens the lower winding of 5. When the mark ceases (1 operated, 2 released), the upper winding of 5 is also de-energized and the selector is released. If a space is too long, 4 and 1 again become operated at the same time and release ensues. Momentary relapses of 1 during a space have no effect. Supply equipment and valve failure. The main switch 102 serves to release the alarms 100 when operated. The receiver anode supply is taken from leads 108 and the filaments 105 of the receiving valves and 81, 91 of the selector valves are connected in series with a barretter 106 in the negative lead, relay 7 being normally operated in this circuit. Operating voltage for the relays 3 and 5 is taken at d on potentiometer 103 while the voltages for the selector valve anodes and timing condensers are taken from an independent potentiometer 104. When any valve filament fails, relay 7 falls back and brings in the alarms 100, but in this case lamp 101 is also illuminated.