MIL-PRF-62488A(AT)
3.3.2.10 Line switch. Audio from a wire telephone line connected to the line terminals
shall be monitored continuously by the intercom channel when the line switch is in the LISTEN
position. When the switch is placed in the TALK position, audio from the intercom channel shall
be transmitted to the telephone line. The switch shall be a spring loaded, momentary type, biased
to the LISTEN position (see 4.5.3).
3.3.2.11 Power interface. Direct current power shall be applied to the distribution unit by
any one of the connected radio sets when the radio is turned on, via pin B of J501, J503, J509, or
J511. An auxiliary power input, J508, shall also be provided to permit use of the intercom
without radios. All power inputs shall be diode isolated to prevent cross coupling between
sources. After a radio is turned on, power-up of the intercom is achieved by setting the power
circuit breaker on the distribution unit to the ON position (see 4.5.3).
3.3.2.12 Power distribution. The distribution unit shall accept supply voltage from pin B
of J501, J503, J509, J511 or J508. The source shall be diode isolated to prevent cross coupling
of power between connectors (see 4.5.3).
3.3.2.13 Retransmission switch. When the retransmission switch is placed in the
RETRANSMISSION position, pin T of J501 shall be connected to pin S of J503, and pin S of
J501 shall be connected to pin T of J503. Likewise, receiver audio from pin K of J501 shall be
directed to pin U of J503, and receiver audio from pin K of J503 shall be directed to pin U of
J501. Receiver audio shall be available for monitoring by crew members at any crew control unit
by selecting the appropriate monitor switches; however, it shall not be possible for any crew
control unit to initiate a radio transmission on the radios connected to J501 or J503 when in the
RETRANSMISSION mode (see 4.5.3).
3.3.3 Interface parts. All interface parts shall be in accordance with Drawing 12310227
(see 4.5.1).
3.4 Performance.
3.4.1 Supply range. The distribution unit shall operate within specifications over a supply
voltage range of 20 to 30 volts (V) dc. The dc power requirement shall not exceed 20 watts (W)
at 26 V dc. The distribution unit shall not be damaged by operation from a supply operating at
worst case limits the following conditions (see 4.5.4.1).
3.4.1.1 Steady-state voltage. Circuit steady-state voltage shall be between 25 and 30 V
for combined generator-battery power supply, 20 to 27 V for battery only condition and no less
than 33 V for generator only condition.
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