Burglar alarm using power cord to transmit signals and method for controlling the same

A burglar alarm using power cord to transmit signals includes a main unit provided with a power supply voltage regulator circuit, a CPU circuit, an FET driving circuit, and an RLC oscillation circuit to convert digital code signals into analog signals, which are amplified and then carried via a power cord; and a wireless decoding horn (2) provided with a power supply voltage regulator circuit (21), a reference voltage circuit (22), an RLC oscillation circuit (23), a comparison circuit (24), a CPU circuit (25), and a horn voice driving circuit (26) to decode and compare a received burglar-alarming signal and drive a horn (27) to make vocal and sounding warnings. The burglar alarm is controlled via different frequencies that represent codes 1 and 0, or a base frequency and different wave widths representing codes 1 and 0, so that the signals could be conveniently carried via the power cord without being interfered by noises on the power cord.