This specification covers Headset-Microphone Kit MK-1039/G. This Headset-Microphone Kit is designed to fit both the regular and large size Combat Vehicle Crewman's Helmet. The electrical characteristics of the kit are ompatible with Tactical Radio Systems, such as the VRC-12. The impedance of the microphone circuit is 150 ohms, and the earphone elements are transformer matched and present a 500-ohm load to the earphone circuit.