Background information and reason(s) for developing the project.

When ones need aid of understanding something that has being said on the TV and worried about the sound might be too loud and disturb others, they might need to using transmitter and receiver circuit with the aid of cordless headphone. 

 For the transmission, this project capable of transmitting the audio signals and converted it to mono, then amplified it and fed to comparator (modulator) stage where there are compared to 90kHz triangle wave (sampling signal). The resulting pulse-width modulating signal (PWM) then drives transistor Q1 to a pulse string of infrared (IR) LEDs. 

 At the receiver, the transmitted signal is picked up by an IR diode and the resulting current pulses converted to voltage pulses converted to voltage pulses and amplified by IC1b and IC1a ( LM833 ). This amplified pulse waveform is then fed through a limiter and filtered to recover the audio waveform.

 This is then fed via volume control VR1 and to output audio amplifier, IC4 (LM386N). IC4 ( LM386N ) is the audio amplifier output stage. It amplifies the signal from volume control and drives a stereo phone jack. 

 The receiver is used either a power from 6V AA alkaline cells battery or rechargeable NiMH (or NiCad) as well. The average current drain is typically around 20mA and so ordinary alkaline dry cells should give at least 80 and up to 100 hours of listening.