As usual, thanks in advance (and I'd be happy to summarize to the net),
Doug Urner, dlu@tektronix
I give each passenger a set of E*A*R plugs, and I wear one in my right ear.
With that, everbody talks loud, and everybody can hear one another.
Al Gettier
They have a volume control in the headset (nice feature) that cannot
be turned all the way down (safety feature).
Sigtronics makes good intercoms too. If you have a yoke-mounted
PTT switch, they will modify their intercom for a nominal fee to
work smoothly with it.