The distance between receiver and transmitter circuit depends on the environment. Light has function to replace cable from audio source to speaker. Transformer X2 is utilized to lock the audio signal. VR1 works as the amplitudo modulator from the T1 signal output.
Parts list :
Resistor R1: 47k ohm
Resistor R2 : 22k ohm
Resistor R3 : 220 ohm
Diode D1-D7 : 1N4001
VR1 : 1k ohm
Polar capacitor C1 : 470 uF/25V
Polar capacitor C2 : 1 uF
Capacitor C3 : 0.1 uF
Transistor T1-T2 : BC148
Transformer X1 : 220 V AC/0-12V AC
X2 : AF output
Transistor SCR1-SCR2 : BA654
