MIL-PRF-58111A(CR)
3.11.1 ICS line. With the selector switch set in any position PVT, ICS, or 1 through 5, a
1.0 KHz signal at 0.6 volts applied to the required pad (see 4.3.7.11f), which is connected to pins
J1-L and J1-M (microphone input) and pin J1-b jumpered to ground, the output across pins J2-R
and J2-S shall be between .35 and .43 volts; this output shall also be the same for any remote
channel selection and also when the HOT MIC-VOX ON-NORM-OFF switch is set to HOT-MIC
or VOX ON with VOX control fully counterclockwise and pin J1-b is ungrounded. HOT MIC
and Interphone key (pin J1-b) operation shall be overridden when any radio channel is selected
and keyed. HOT MIC and VOX ON shall be overridden when PVT is selected and J1-A or J1-d
is jumpered to ground.
3.11.2 PVT line. With the selector switch set in PVT position, a 1.0 KHz signal at 0.6
volts applied to the required pad (see 4.3.7.11f), to pins J1-L and J1-M (microphone input), the
output across pins J2-q and J2-P shall be between .35 and .43 volts when pin J1-A is Jumpered to
ground (J1-c). Pin J1-A may be grounded in the aircraft wiring to provide automatic HOT MIC
activation when selector switch is set to PVT.
3.11.3 ICS off. Any ICS signal to the headset shall be reduced at least 60 dB when
switch is set to ICS OFF position.
3.12 Sidetone. With selector switch set to ICS position, HOT MIC-VOX ON-NORM-
ICS OFF switch to NORM position, pin J1-d or J1-b jumpered to ground and 1.0 KHz signal at
0.6 Volts applied to the required pad, the output voltage across pins J2-D and J2-E shall be -4.0
to -6.0 dB below the level obtained across J2-D and J2-E when a 0.39 volt rms, 1.0 KHz signal is
applied to pins J2-R and J2-S. A comparable sidetone reduction shall occur when selector switch
is set to PVT and pin J1-A is jumpered to ground.
3.13 Response, microphone amp. The frequency response shall not vary more than ±1.0
dB within the frequency range of 700 Hz to 2250 Hz. The 3 dB ±1.0 dB bandwidth shall be 350
Hz to 4500 Hz. The 1 dB and 3 dB ± 1 dB levels are referenced to the level at 1 kHz. The
amplitude between 350 Hz and 4500 Hz shall be no greater than 1 dB above the amplitude at 1
KHz. The slope of the asymptotic attenuation curve above 4500 HZ and below 350 Hz shall be
no less than 6 dB per octave.
3.13.1 Response, wideband audio out. The frequency response shall not vary more than
±1.0 dB in the range 200 to 3000 Hz. The 3 dB ± 1 dB bandwidth shall be 100 to 6000 Hz.
These levels are referenced to the 1 KHz level. The slope of the asymptotic attenuation curve
above 6000 and below 100 should be no less than 6 dB per octave.
3.14 Distortion, microphone amp. The total harmonic distortion shall not exceed three
(3) percent with a signal level of 0.6 volts applied to the required pad and five (5) percent with a
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