The first version was a single switch meaning "command them all", and that is
wrong the moment a station has three: two SPE on a combiner and a PowerGenius
on another antenna would all go into OPERATE together, keying an amplifier that
has nothing to do with the pair.
It is now a set. Each amplifier is ticked into the group or not, the group is
stored as a list of ids, and an amplifier outside it keeps its own buttons —
which is the entire point of it being a set.
A group of fewer than two members is stored as none: one amplifier coupled to
itself would make every command fan out to a single member for ever.
A remembered member that is no longer running is skipped rather than failing
the command — deleting one amplifier must not break the button on the other.
An amplifier saved without an id cannot join, and the panel says so instead of
quietly omitting it from the list.
The SPE CO1-2 combiner is an RF device: it sums two amplifiers and commands
nothing. So "combined" operation is really two amplifiers that must be held in
the same state, and one left in STANDBY while the other keys means the combiner
sees power on a single input.
A switch in Settings → Amplifier makes ON, OFF and OPERATE act on every
configured amplifier. Offered only with two or more: coupling one amplifier to
itself is a switch that cannot do anything.
The METERS stay per amplifier, deliberately. Two amps combined are still two
amps, and an operator watching for one of them to run away needs to see them
apart — a summed bar would hide exactly the fault worth catching.
Fanned out in AmpOperate/AmpPower rather than in the UI: the card and the docked
widget both call these, and a coupling built into one would be missing from the
other, which on a combiner means one amplifier keyed and one not. The clicked
amplifier goes first, so a partial failure still did what the operator asked
before it stopped.
While linked, an amplifier with no power command — a PGXL on its direct link —
is skipped silently rather than reported: it would make a successful pair look
broken.