The NOR-gate circuit referred to below is exactly what I built up a few
years ago for a reliable hardware interlock between two radios. I use if
for SO2R CW and RTTY as well as MS where we have two interlocked radios
keying a single transmitter. This allows two ops to listen to different
parts of a pileup and "race" for the next QSO, the first one locking out the
other.
My lockout box uses a quad NOR gate, 8 resistors, 2 NPN transistors and a
DPDT switch for selecting different states (FOW, Key 1 wins and
independent). No diodes, so curious what those might be used for.
Ed W0YK
Joe W4TV wrote:
> The bigger problem - more critical need for interlock - is
> those configurations using separate computers for each rig.
> In those cases the only reliable means is to connect a
> normally closed relay in series with PTT to each rig and use
> the amplifier PTT line from one rig to activate (open) the
> relay on the other rig when transmitting. A circuit with an
> equivalent function for two radios can be built with one IC
> (a quad NOR package), two diodes, a few resistors and two NPN
> transistors.
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