GB1131801A - Remote control systems - Google Patents

Abstract

1,131,801. Radio signalling. ELLIOTT & EVANS Inc., [trading as TELECTRON CO. DIVISION OF ELLIOTT & EVANS Inc.]. 25 Jan., 1966, No. 3369/66. Heading H4L. In a remote control system the transmitter radiates a signal modulated sequentially by two different modulation frequencies and the receiver provides two separate output signals in response to the two modulation frequencies, means being provided to prevent the simultaneous provision of the two output signals if the two modulation frequencies are present simultaneously and further means being provided to prolong the duration of the first of the output signals so that the two output signals overlap in time. Transmitter, Fig. 3.-Momentary closing of switch 48 energizes the carrier generator 20, which is modulated at an audio frequency by circuit 60, 68, and at the same time a storage capacitor 72 is charged. When the switch 48 is released a further capacitor 70 is shunted across winding 60, so that the carrier is modulated at a different audio frequency, the oscillations being maintained for a short period by the charge on capacitor 72. In a modification, Fig. 4 (not shown), closing of a switch causes a complete operating cycle, the R.F. oscillator being initially modulated at a first audio-frequency and time-dealy means allowing a second A/F modulating circuit to function after a predetermined delay, the depth of modulation due to this second circuit being so much greater than that due to the first audio frequency that the first audio-frequency modulation is swamped. Receiver, Fig. 2.-The received signal is detected by a super-regenerative receiver 76, amplified at 150 and supplied to parallel amplifiers 168, 170, whose outputs are supplied to tuned circuits 82, 84 tuned to the first and second audio-frequencies respectively. An output from circuit 82 is rectified at 192 to charge capacitor 202. At the same time the signal developed across resistor 184 is rectified at 190 to charge capacitor 198. The charges on the two capacitors are of opposite polarity and when the frequency of the input signal differs from the resonant frequency of circuit 82, the voltage across capacitor 198 exceeds that across capacitor 202. Similarly the voltage across capacitor 202 exceeds that across capacitor 198 when the input signal is at the resonant frequency of circuit 82. Thus the potential on line 188 will change from negative to positive when the correct audio-frequency signal is received, circuit 84 operating in the same manner to change the potential on its corresponding output line, test jacks 208, 210 being provided. When the potential on line 188 changes to positive, non-conductive valve 230 is biased to conduct to energize relay 240 and charge capacitor 96, valve 228 being held non- conductive. When the positive potential ceases on line 188 and appears on the other output line, valve 288 conducts to energize relay 236, and valve 230 becomes non-conductive. However, the charge on capacitor 96 maintains relay 240 energized for a period overlapping the energization of relay 236.