MIL-DTL-83511/5A
Microphone: M-87/AIC, in accordance with MIL-PRF-26542 and MIL-PRF-26542/2.
Microphone boom: 1 required, USAF drawing 67B1854 or equal.
Cord data:
Amplifier to terminal of main cord: 16.00 inches (408.4 mm).
Terminal to U-384/U main cord: 10.00 inches (254.0 mm).
U-385/U to switch: 26.00 inches (660.4 mm).
Switch to connector: 51.00 inches (1295.4 mm).
Specification: MIL-DTL-55668 type 2, 5 conductor tinsel rubber jacket.
Microphone transistorized amplifier.
Operating temperature: The transistorized amplifier shall operate in temperatures between -0 to
+50°C.
Output impedance: The output impedance of the amplifier shall be such that it operates
satisfactorily into the input microphone circuit of radio control unit C-1138 A/UR or equivalent circuit
(test circuit see figure 2).
Frequency response: The output of the microphone amplifier at 1,000 Hz when connected to the test
circuit shall be 30 ±5 dB above a zero reference level of one millivolt; the input shall be 28 dynes/cm
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(103 dB relative to 0.0002 dynes/cm ) applied 0.25 inch (6.35 mm) from the microphone. A dip
between 1,100 and 1,700 Hz not more than 150 Hz wide and not to exceed the lower limits by more
than 7.5 dB is allowable.
a. Response variate - After the environmental tests; the microphone amplifier shall not vary more
than 4 dB from its initial response at the frequency between 300 and 4,500 Hz.
Intermodulation distortion: Intermodulation distortion tests shall be performed on the microphone
amplifier using two tones at 700 and 1,000 Hz., each tone to be equal in sound pressure levels relative
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to 0.0002 dynes/cm at the output of the microphone amplifier the total harmonic and intermodulation
products shall not be greater than 35 dB below the output level of the total test tones with an input
sound pressure level of 103 dB and not greater than 32 dB below the level of the total output test tones
with an input sound pressure of 110 dB.
a. Distortion variation: After environmental tests, the variations of harmonics and intermodulation
products shall not be greater than 35 dB below the level of test tones with an input of 103 dB and
30 dB below the level of the other test tone inputs with an input of 100 dB.
Belt (clothing) clip: Roanwell Corp. P/N 20860 or equal.
Microphone amplifier: Roanwell Corp. P/N 657-010-002-000 or equal such as AM357B.
Output impedance: Operates satisfactorily into input microphone circuit of radio control unit
C-1138/UR.
Frequency response: 300 to 4,500 Hz.
Wiring schematic: See figure 3.
Bar switch: In accordance with MIL-DTL-83511 and this specification sheet (see figure 4).
Switch and housing:
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