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 compatible with Tactical Radio Systems, such as the VRC-12.

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MIL-DTL-55535A

AMERICAN NATIONAL STANDARDS INSTITUTE

Measurement Microphones � Part 2: Primary Method for Pressure

Calibration of Laboratory Standard Microphones by the Reciprocity

Technique

(Copies of these documents are available from https://www.ansi.org or the American National Standards

Institute (ANSI), 25 West 43rd Street, 4th floor, New York, NY 10036).

NATIONAL CONFERENCE OF STANDARDS LABORATORIES (NCLS)

Calibration Laboratories and Measuring and Test Equipment - General

Requirements-Replaces Mil-Std-45662

(Copies of these documents are available from https://www.ncsli.org or to National Conference of

Standards Laboratories (NCSL), 2995 Wilderness Place, Suite 107, Boulder, CO 80301-5404.)

2.4 Order of precedence. In the event of a conflict between the text of this document and the

references cited herein, the text of this document takes precedence. Nothing in this document, however,

supersedes applicable laws and regulations unless a specific exemption has been obtained.

3. REQUIREMENTS

3.1 Description. Headset-Microphone Kit MK-1039/G consists of the component parts listed in 1.2.

The dynamic earphones H-269/G are waterproof and blast proof. The dynamic, noise canceling

microphone and boom assembly M-138/G is waterproof and blast proof. Switching facilities are provided,

which permit the user to communicate over the vehicle intercommunication system or over the vehicle

tactical radio system. Headset-Microphone Kit MK-1039/G will fit both the regular and large size Combat

Vehicle Crewman's Helmet.

3.2 First article (see 4.3). When specified (see 6.2), a sample shall be subjected to first article

inspection.

3.3 Parts, materials and processes; general.

3.3.1 Magnetized materials. The materials used in the magnetic circuit shall be of such a character

and shall be so processed and assembled that the microphone and earphone elements will not suffer

objectionable degradation in performance, due to loss in magnetization over long periods of storage or

service.

3.3.2 Diaphragm and air gap. The stability of diaphragm material and the concentricity of the air gap

shall not be affected by extended aging and exposure to environmental conditions. There shall be no

foreign material present in the air gap.

3.3.3 Pure tin. The use of pure tin, as an underplate or final finish, is prohibited both internally and

externally. Tin content of loudspeaker components and solder shall not exceed 97 percent, by mass. Tin

shall be alloyed with a minimum of 3 percent lead, by mass (see 6.8).

3.3.4 Recycled, recovered, or environmentally preferable materials. Recycled, recovered, or

environmentally preferable materials should be used to the maximum extent possible, provided that the

material meets or exceeds the operational and maintenance requirements, and promotes economically

advantageous life cycle costs.