Powerline Carrier-Current Remote Control or Intercom

Using 567 IC tone decoder/detector, we can build a remote control and or intercom. This circuit can be used to control a relay, or to carry an audio signal (intercom) through power-line wiring. Here is the schematic diagram of this remote control/intercom circuit:

The relay will be activated if you inject a 100kHz tone. This can be used to control a remote lighting. For example, for light jockey application, you can  build three similar circuits but with different frequency (100kHz, 150kHz, 200kHz) to control red, blue, and green stage lamps. The frequency is determined by R1 and C1 values, with frequency=1/(1.1 x C1 x R1) [Circuit’s schematic diagram source: Philips Semiconductors Application Notes]