An X10 controller creates a 121 kHz carrier, superimposed on the 60 hZ AC line. At the 60 hZ 0 crossing, the system sends pulses of that carrier frequency, containing an address and a command. The address tells which remote X10 device to respond, and the command tells it how to respond.
An X10 wireless system consists of an RF transmitter, that sends a code to an X10 transceiver. The transceiver receives the RF, decodes it into address and command, and then operates the same way as the controller. In addition, the transceiver can act as an X10 remote device, controlling whatever is connected to it according the command whenever it is addressed. to send pulses out to the X10 devices.