Patent GB-533136-A (GB)
Title: Improvements in remote control system for wave-signal receivers
IPC: H03J5/24
Filed: 1939-10-12
Abstract: 533,136. Electric control systems. HAZELTINE CORPORATION. Oct. 12, 1939, No. 27767. Convention date, Oct. 22, 1938. [Class 40 (i)] A radio receiver is remotely controlled by manually varying the frequency of a highfrequency oscillator, and transmitting the oscillations over the power and supply mains to the receiver, an adjustable frequency follower being provided at the receiver, and a tuning motor being driven in accordance with the difference between the generated high-frequency oscillations and the output of the frequency follower. The radio receiver 10 is controlled by a remote-control unit 11 actuating a tuning control unit 12 and a unit 13 controlling the on-off switch 9 and volume control 17, the units 12, 13 being adjacent to the receiver. An oscillator 20 is contained in the remotecontrol unit 11 and an oscillator-modulator 21 is contained in the unit 12, the frequency of each oscillator being adjustable in steps and the tuning of the receiver being dependent on the difference frequency of the generated oscillations. The oscillator frequency-determining circuit is connected to the control grid of the oscillator valve 22 and comprises an inductance 23 tuned by a condenser 24 and any one of a set of condensers 25 ... 29, which can be selectively connected in parallel with the condenser 24 by push-button switches 35 ... 39. The second grid of the valve 22 is utilized as an oscillator anode and is connected to a feed-back circuit comprising an inductance 43 inductively coupled to the inductance 23. The output of the oscillator section of the valve 22 is electronically coupled to the anode-cathode circuit which is coupled to the power-supply mains 19 through a band-pass filter including a transformer 45 the primary winding of which is tuned by a condenser 46, which may be formed wholly or in part by the inherent capacitance of the output circuit of the valve 22. Remote volume control is effected by condensers 47, 48, which tune the secondary winding of the transformer 45 when condensers 47<SP>1</SP>, 48<SP>1</SP>, respectively, are included in the circuit of the oscillator. The condensers 47, 47<SP>1</SP>, 48, 48<SP>1</SP> may be connected in their appropriate circuits by means of push-button switches 51, 52. A switch 54, connecting the tuned transformer 45 to the supply mains 19, is unicontrolled with the push-buttons 35 ... 39 and 51, 52 so as to be closed only when a control operation is being effected. The tuning-control unit 12 comprises a tuning-motor 60 operating the ganged switches of the condenser sets 16, 16<SP>1</SP> by means of reduction gears. Power is supplied to the motor 60 through a thermostatic switch 61, having a heater 62, and the normally closed contacts 63 of a relay 64. The high-frequency tuning-control signals are transmitted over the power line 19 to the section 12 and applied through a transformer 65 to the grid of a frequency-changer 66. The primary winding of the transformer 65 is series-tuned by means of condensers 67, 67<SP>1</SP> and the secondary winding is tuned by a condenser 68 and loaded by a resistor 68<SP>1</SP>. The selector so formed is arranged to pass a band of frequencies including those generated by the oscillator 20 when any of the push-buttons 35 ... 39 are operated and to reject the frequencies generated when the pushbuttons 51, 52 are operated for effecting volume control. The frequency-converter or oscillatormodulator 21 comprises an oscillator section for generating oscillations the frequency of which is variable in steps corresponding to those of the oscillator 20 by means of an inductance 70, a condenser 71 and any of condensers 72 ... 76 adapted to be selectively connected in parallel with the condenser 71 by a switch 77 driven by the motor 60. The oscillator section also includes a feed-back circuit comprising an inductance 78 coupled to the inductance 70. The motor 60 is operated by the beat-frequency comprising the difference between the frequencies of the oscillators 20, 21 by means of a triode rectifier 79 coupled to the output of the frequency changer 66 and adapted to energize the relay 64. The volume-control unit 13 includes a motor 90 coupled to the volume-control potentiometer 17 and the on-off switch 9 of the receiver 10. The motor 90 is reversible and is controlled by reversing relays 91, 92 through contacts 93, 95. When it is desired to operate the receiver the push-button 51 is operated and the switch 54 simultaneously closed. The oscillator 20 delivers highfrequency oscillations of a pre-determined frequency, to which a series-tuned circuit 100, 101, 102 is resonant and energizes the relay 91 so as to operate the motor 90 in a direction to close the switch 9 and turn up the volume control 17. The thermostatic relay 61, 62 closes a pre-determined time after the energization of the primary winding of the transformer 18 through the switch 9. During this interval the valves 66, 79 are heated and, provided no control signal is applied to the valve 66, the valve 79 draws sufficient anode current to open the relay contact 63. Depression of the pushbutton 52 similarly causes reverse rotation of the motor by means of a series-tuned circuit 107, 108,109 and relay 92. As shown the pushbutton switch 37 has been operated and the receiver is tuned to the corresponding station. The oscillations of the oscillator-modulator 21 are of the same frequency as those of the oscillator 20 and the beat frequency generated is zero. There is no input to the grid-leak detector 79, which therefore has a high conductance and energizes the relay 64 which opens the motor circuit at the contacts 63. If another tuning control push-button is operated, a frequency difference between the two oscillators occurs and the modulator has a beat frequency output which biasses the valve 79 and deenergizes the relay 64 to close its contacts 63 and start the motor 60. The contacts of the switch 77 are closed consecutively until the frequency of the oscillator 21, is again equal to that of the oscillator 20. Instead of transmitting the control oscillations over the power lines 19, a separate cable may be used or they may be transmitted by radiation. The frequency follower may alternatively comprise a passive electrical network with suitable frequency-responsive control apparatus.