How ‘bout something like a chess timer?
The timers is reset. The Moderator asks a question to a candidate (then shuts up!). The candidate addressed hits his timer button and can talk until time runs out or he hits the button again.
At that point the second candidate can hit his button and respond until he is done or his timer runs out.
IF the first candidate still has time remaining, he can respond.
And back and forth it goes until both candidates are out of time. Then clocks are reset and the next question is asked.
Microphones only work if the candidates timer is running.
Maybe start with 5 minutes per candidate per question? That way they can get up to 6 questions in an hour.
And the moderator’s microphone should shut off while a candidates mike is active!
Liberals make up the rules. Good little Conservatives try to figure out how to adapt to the made-up rules. Then rules beget rules, then Conservatives try to figure out how to adapt to the new rules. We never learn.