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

3.7.3 Overload. The earphone shall show no more than 3 dB change from its original response curve,

after being subjected to the test specified in 4.8.4.

3.7.4 Dielectric strength, and insulation resistance. There shall be no evidence of insulation

breakdown. There shall be no decrease in insulation resistance below 1 megohm following the test (see

3.7.5 Impedance. The impedance of the earphone at 1,000 Hz shall be 15 ohms � 20 percent, as

determined by the test (see 4.8.2).

3.8 Service conditions. The equipment shall meet the following service conditions. Where a test is

referenced, meeting the test shall be considered as compliance with requirement.

3.8.1 Temperature (see 4.13.1).

a. Operating: Ambient temperature in the range of + 150� to � 40� F (Fahrenheit). (The + 150� F

temperature includes affect of sun-load). Exposure at the high temperature extreme not to

exceed 4 hours, and at the low temperature extreme not to exceed 72 hours, at any one time.

b. Non-operating: Exposure in the range of + 160� to � 80� F; exposure at the high temperature

extreme not to exceed 4 hours and at the low temperature extreme not to exceed 24 hours.

3.8.2 Moisture resistance. Equipment shall meet specified performance after subjection to the test in

4.13.2. The equipment shall meet the microphone and earphone response requirements of 3.6.1 and

3.7.1 with degradation not to exceed 3 dB. There shall be no evidence of cracking, warping, or other

mechanical deterioration.

3.8.3 Altitude (see 4.13.3). The response characteristics of the earphone and microphone shall be

measured, and shall not exhibit degradation in performance in excess of 5 dB from the requirements of

3.6.1 and 3.7.1 after being subjected to the following tests.

a. Operating: Up to 15,000 feet (16.7 inches of mercury) above sea level.

b. Non-operating: Up to 50,000 feet (3.4 inches of mercury) above sea level.

3.8.4 Immersion (see 4.13.4). After completion of an immersion in water at a depth of three feet for 2

hours, any evidence of water in the switch cavity shall be cause for rejection. The microphone and

earphone shall then meet the requirements of 3.6.1 and 3.7.1, respectively.

3.8.5 Salt atmosphere (see 4.13.5). Upon completion of the test, there shall be no evidence of harmful

corrosive action or damage due to the salt spray. The earphone and microphone shall not suffer any

degradation in response in excess of 3 dB from their initial performance values of 3.6.1 and 3.7.1.

3.8.6 Blast (see 4.13.6). Following the blast test, the earphone and microphone units shall not suffer

any degradation in their response of more than 3 dB from the initial performance values of 3.6.1 and