PURPOSE: To control the analog value of sound volume by remote operation by selecting and supplying a voltage, which corresponds to the pulse number of a rotary switch on the operation side, to an equipment to be operated.

CONSTITUTION: As the slider of the switch is positioned at a certain position by being turned clockwise, pulses that correspond to the position are counted by counter 21. At the same time, oscillator 24 sends four pulses and parallel input data of parallel-series shift register 22, i.e. the number that slider 17 indicates is converted into a serial signal, which is sent to driver circuit 25. This signal is transmitted by infrared rays. The data received by the equipment side enter series- parallel shift register 33, which stores them as parallel four-bit signals. Each signal is decomposed through decoder 34 and its output is passed through one of preset resistances R1∼R16 to extract a voltage that corresponds to each number.