A partir de uma pesquisa rápida, é isso que eu juntei da memória alfa da Star Trek Wikia.
link
Eu não acho que seja claramente indicado que forma de comunicação ele usa, mas há algumas limitações, como alcance.
The Starfleet combadge was a crystalline composite of gold,
microfilament, silicon, beryllium, and carbon-70. (TNG: "The Last
Outpost", "Time's Arrow"; VOY: "Hope and Fear") Due to the size of the
combadge, its working range was limited to five hundred kilometers,
although a starship could boost the signal to bridge larger distances.
(TNG: "11001001")
Também não há menção explícita do que está "sob o capô", exceto o que é composto e o que o combadge pode ser modificado / desmontado para alcançar.
In emergency situations, a combadge could be modified for use in other
applications. It could be converted into a subspace distress beacon,
or the tiny power cell could be extracted for other uses. (DS9: "Rocks
and Shoals") Lieutenant Worf used it to power a homemade field
generator for several seconds. (TNG: "A Fistful of Datas") In 2374,
Captain Kathryn Janeway of the USS Voyager was able to modify Seven of
Nine's Borg implants to escape the brig of the USS Dauntless using
pieces of her combadge. (VOY: "Hope and Fear") If the casing of the
combadge was ever cracked, an emergency distress signal was emitted,
mainly to help searchers locate victims. (TNG: "A Fistful of Datas";
VOY: "Time and Again") Combadges, when destroyed by an electrical
force, could cause damage to the wearer's clothing. (TNG: "Thine Own
Self")
Até onde eu sei, não mudou muita coisa nos combadges além dos designs.
Foto de combadge do 2360.
Foto de 2370's of combadge