Patent GB-535385-A (GB)
Title: Improvements in or relating to the remote control of radio transmitters and receivers
IPC: H03J7/16
Filed: 1939-10-06
Abstract: 535,385. Electric control systems. STANDARD TELEPHONES & CABLES, Ltd., BEATTY, W. A., and SCULLY, C. T. Oct. 6, 1939, No. 27370. [Class 40(i)] In a radio receiver or transmitter incorporating a remote control system as described in Specification 521,710, wherein the tuning motor as soon as it is energized upon change of frequency. of the control wave operates in a sense to bring the auxiliary tuned circuit into resonance at the new control frequency, a frequency error detector circuit is associated with the auxiliary tuned circuit or a frequency changer coupled thereto and controls the currents through a pair of amplifier valves differentially according to the direction in which'the control frequency is changed. Terminals 51, 52 are the input connections to a tuning error detector circuit comprising diodes 53, 54 associated with tuned circuits 57, 58 and 60, 61 tuned to 455 and 465 kc. respectively, the normal intermediate frequency being 460 kc. These circuits are connected through resistors 63. 64 to the grids of amplifying valves 65, 66, in the anode circuits of which are relay windings. 69, 70 controlling normally open contacts 84, 86 and normally closed contacts 85, 87. These contacts 84, 86 control field winding circuits of the controlled motor, closing of the contact 84 causing clockwise rotation and closing of the contact 86 causing counter-clockwise rotation. In order to prevent short-circuiting of the windings if both contacts 84, 86 should close simultaneously the circuit through the contacts 84 is completed through back contacts of contacts 86 and the circuit through the contacts 86 is completed through back contacts of contacts 84. Should both contacts 84, 86 be simultaneously closed or opened the motor cannot rotate. The back contacts 85 are connected in parallel with the front contacts 87, the back contacts 87 being in parallel with the front contacts 85 so that if both pairs of front contacts are closed resistors 78, 79 are short-circuited removing the cut-off bias and allowing the valves 65, 66 to remain in a sensitive condition. If one relay only is operative, the corresponding resistance 'is short-circuited. Should a remote control operation be completed and the remote oscillator be switched off, the valves 65, 66 will no longer be driven negative and both relays assume the operative condition. The motor then does not rotate, but the valves 65, 66 are in a sensitive condition for further control operations. The operation of switching off the control oscillator may cause an auxiliary switching operation at the controlled apparatus, for example an auxiliary circuit aperiodic in the range of frequencies of the control oscillator may be arranged to de-energize a relay. The error detector circuit may be connected in the receiver for tuning correction during reception and associated with the auxiliary tuned circuit when the control oscillator is switched on. When transmitting control frequencies over supply mains, the control oscillator may use a comparatively low frequency which may be passed through a frequency multiplier at the controlled apparatus.