Mains Remote Transmitter

This circuit can be used to superimpose a 143-kHz carrier on the mains voltage, which allows various applications to be realised. One example is the ‘Mains Remote Switch’. Besides the power supply, the circuit consists of only a sine-wave oscillator, a buffer stage and an output transformer for isolation from the mains network.The oscillator, which is built around IC1a, is a standard Wienbridge design whose frequency is determined by R1, C1, R2 and C2. The combination of R3, R4 and the amplitude stabilisation circuitry built around T1 provides a gain of 3.