Line Carrier Link (December 1997): The receiver unit's overlay diagram
and parts list should show R15 (in series with the relay coil) as 120 ohms
rather than 1.2k. Also D5 in the receiver overlay diagram is shown the wrong
way around, and strictly speaking, the address programming links (LK1 to
LK4) should match the code example code used in the transmitter - this can
be corrected by changing the positions of LK1 and LK3.
If the mains supply used for the link is rather noisy, you may find that
while the signal is being received (the 'carrier signal' LED flashes) the
codes are not detected correctly, leading to an erratic response. In this
case, you will need slow the response of the clock detecting circuit (based
on Q1) in both the transmitter and receiver. This can be done by changing Q1
to a BC338-type transistor (it has lower gain and bandwidth), or adding a
47nF capacitor across collector load of Q1.