IR transmitter uses two-stage transistor amplifier to drive two series-connected IR LEDs. An audio output
transformer is used (in reverse) to couple audio output from TV to the IR transmitter.Transistors T1 and T2
amplify the audio signals received from TV through the audio transformer. Low impedance output windings (lower gauge or thicker wires) are used for connection to TV side while high-impedance windings are connected to IR transmitter. This IR transmitter can be powered from a 9-volt mains adapter or battery.
Red LED1 in transmitter circuit functions as a zener diode (0.65V) as well as supply-on indicator. IR receiver uses 3-stage transistor amplifier. The first two transistors (T4 and T5) form audio signal amplifier
while the third transistor T6 is used to drive a headphone. Adjust potmeter VR2 for max. clarity. Direct photo-transistor towards IR LEDs of transmitter for max. range. A 9-volt battery can be used with receiver
for portable operation. ( via EFY )