Volume control is also standard, along with corrosion-resistant brass plugs.
Extra life is added to all cables and connectors by shielding them and providing a strain-relief nylon core. The IIsx, III and IIId operate on aircraft or battery power and will expand to four places with SR-4 expasion module. The 403 and 403d will expand to six places. To prevent cockpit clutter, all extraneous cords are detachable. And for your safety, Flightcom has designed each intercom to be fail-safe.