Jim Logajan writes:

Just tell people they would operate it like a telephone: the pilot would
direct her call to a particular listener (e.g. ATC) and ATC gets a signal
(like a phone ringing!) and can let it ring until they have time to answer
the call. But in a pinch, the system could also act like a party line system
and after hitting the emergency transmit button in her aircraft, the pilot's
distress call would automatically cut in over less-urgent calls to not only
ATC, but to any aircraft who have set their receivers to automatically accept
emergency calls.

In essence, digital systems provide multiple virtual private circuits if
needed, but still allow broadcast or "party" line equivalents for situations
where that communication mode is more useful.

What about analog users? What if an analog user transmits while a
queued message is being transmitted?

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