Remote control ultrasonic signal transmitter - has capacitors connected to tuned circuit of oscillator over diode and via switches

摘要

The ultrasonic signal transmitter can be used for the remote control of TVs, domestic lighting, etc. It consists of an oscillator circuit coupled to a parallel tuned circuit. Switches connect and disconnect capacitors to and from the tuned circuit in order to generate different frequencies, and switch on and off supply voltage to the oscillator circuit. It also includes an ultrasonic transmitter. Each of the connectable capacitors (17, 18) is connected to the tuned circuit (8-10) through a diode (14, 16), and can be connected to a.c. wire to the tuned circuit through a switching component (11-15) with only one current path. The switching component also connects the ultrasonic transmitter (20) directly to the tuned circuit.