Heil AD-1-IM Headset Adapter W/Cap for HC Use on Icom Modular. AD-1 series cables are required for the Heil boom microphone headset model. All Heil Headset Adapter Cables use commercial-grade microphone connectors with dual-exit cable clamps. If you have several brands of transceivers, individual adapter cables may be connected to each radio, so you may quickly and easily move your Heil boom microphone headset from one transceiver to another. They have a capacitor in series.