The designer of this
circuit had fitted two (waterproof) loudspeakers in his bathroom and
connected them to the stereo system in the living room via a long cable.
Naturally, this promptly led to the desire to be able to use the remote
control unit from the bathroom. Commercially available extension sets
for this purpose were judged to be unsatisfactory, primarily because
they require an additional IR transmitter diode to be fitted in front of
the amplifier. Although the repeater shown here requires a length of
coaxial cable, it provides a simpler, and above all more reliable,
solution to the problem. The signal transmitted by the remote control
unit is received by IR receiver IC2, and the (nearly) open-collector
output of T1 is connected to the RC5 bus of the stereo system.
This proved to work excellently with Philips equipment, and it will
probably also work with equipment from other manufacturers with a few
small modifications. Voltage regulator IC1 is used here to allow the
supply voltage to range from 8V to 30V, and diode D1 provides protection
against a reverse-polarity supply voltage connection. A nice side
benefit arose from the fact that the loudspeakers in question (Conrad
models) have transparent cones and protection grilles with rather large
openings. This made it possible to ﬁt the tiny circuit, which was built
on a piece of prototyping board, to the frame of one of the speakers,
behind the cone. The whole arrangement is thus hidden, but the remote
control still works perfectly if it is aimed towards the speakers.