Patent GB-1478485-A (GB)
Title: Control information signal transmitting and receiving arrangements
IPC: H04B1/20
Filed: 1974-08-21
Abstract: 1478485 Controlling by sound; remote control SONY CORP 21 Aug 1974 [23 Aug 1973] 36747/74 Headings G4F and G4H [Also in Divisions H3-H4] In an information transmitting and receiving arrangement including a transmitter T and at least one receiver R, the transmitter comprises means 6 for frequency or amplitude modulating first and second carrier signals from 4 and 5 with a first remote control signal, means 7 for frequency modulating the first carrier signal with a second remote control signal and means 8 for frequency modulating the second carrier signal with a third remote control signal, the first and second carriers are transmitted by 12 to the receiver R and a demodulator 21-23 and 26-28 derives the first, second and third remote control signals from the first and second carrier signals. Variable resistors 7 and 8 enable variation of the carrier frequencies f 1  and f 2  of astable multivibrators forming modulators 4 and 5 such that f 1  = 35Œ2À8 kHz and f 2  = 50Œ4 kHz. The outputs from the modulators 4, 5 are mixed with the output from a microphone 1 in a mixer 11 and transmitted by a transmitter 12 at 44 MHz. The receiver R includes an RF amplifier and mixer 15, a frequency discriminator 17 and a muting circuit 18. The 35 kHz and 40 kHz are regained by BPF's 21 and 26 whose outputs feed via limiters 22, 27 and frequency discriminator 23, 28, HPF's 24, 29 and LPF's 31, 32. The output frequencies from the HPF's 24 and 29 are higher than 500 Hz and amplitude detectors 25, 30 provide no outputs when switches 9 and 10 at the transmitter T are off and and provide outputs when the switches 9 and 10 are on. The outputs +b, -b and +a, -a from the LPF's 31, 32 are provided for signals frequencies less than 500 Hz and the levels at the outputs of the LPF's 31 and 32 are varied in accordance to the resistance values of resistors 7 and 8 at the transmitter T. By controlling f 1  and f 2  by adjusting resistors 7 and 8 the levels of the left front and back signals and the right front and back signals of the stereo reproducing apparatus 51 can be differentially adjusted by control of the channel balance by control of AGC amplifiers 43, 45, 47  and 49. By control of switches 9 and 10 a frequency f 3 =500 Hz from an oscillator 6 is supplied to amplitude or frequency modulate carrier signals f 1  and/or f 2  of the modulators 4 and/or 5. When switch 9 or 10 is on selective control signals are obtained at the receiver R to provide up and down control of the master volume to all channels of the apparatus 51 as obtained by control of AGC amplifiers 43, 45, 47 and 49, An output up to 15 kHz from a LPF 20 corresponds to that from the microphone 1 and when both switches 9 and 10 are on this provides microphone on or off control signals to the receiver so that the microphone signal from IPF 20 is mixed or not in mixers 42, 44, 46 and 48 with quadraphonic signals T 1LF , T 1RF , T 1LB  and T 1RB . A logic circuit 50 includes NOT circuits 33, 34, 41, AND circuits 35, 36, 38, a flip-flop 37, on OR circuit 39 and a switching circuit 40 and provides a control or pulse signal at the output of NOT circuit 41 to control the up and down of the master volume to the AGC amplifiers 43, 45, 47 and 49. The logic circuits 50 provides a further output at flipflop 37 to control the input on and off of the output from the microphone 1 in response to the outputs from the detectors 25 and 30. Ultrasonic waves or a light source can be used instead of the electromagnetic wave used as the transmitting wave from transmitter 12 described above.