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Using this low-cost project
one can reproduce audio from TV without disturbing others.
It does not use any wire connection between TV and headphones.
In place of a pair of wires, it uses invisible infrared
light to transmit audio signals from TV to headphones.
Without using any lens, a range of up to 6 metres is
possible. Range can be extended by using lenses and
reflectors with IR sensors comprising transmitters and
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.
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.
towards IR LEDs of transmitter for max. range. A 9-volt
battery can be used with receiver for portable operation.
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