TM 55-1510-220-10
Figure 3-1. Audio Control Panel (C-499) (Typical Pilot, Copilot)
(e)
No. 5. On connects user's head-set to
audio from No. 2 UHF and VOW transceivers.
(3)
NAV radio monitor controls. Combination
volume control and "ON-OFF" switches for NAV receivers.
(a)
NAV-A. On connects user's head-set to
audio from VOR-1, VOR-2 or marker beacon set in use.
(b)
NAV-B. On connects user's head-set to
audio from TACAN or ADF set in use.
c.
Controls and Functions.
(1)
Microphone Impedance Matching Switch.
Two-position, thumb-actuated switch. Selects Interface
circuit that best matches impedance of microphone in use.
(a)
The impedance of MIC 1 position is 5
Ohms.
(b)
The impedance of MIC 2 position is
150 Ohms.
(2)
Microphone Selector Switch. Controls
activation of microphones.
(a)
HOT
MIC.
Admits
speech
to
interphone system without need to key selected microphone.
(b)
NORM. Blocks speech from interphone
system unless selected microphone is keyed.
c.
ICS OFF. Deactivates microphones.
d.
Controls and Functions.
(1)
Transmitter-interphone
selector
switch.
Connects microphone and headset to selected radio
transmitter or Interphone. Bypasses control of respective
receiver audio switch.
(a) PVT. Activates pilot-to-copilot private
Intercom.
(b)
ICS. Activates interphone for pilot,
copilot, and mission avionics operator communications. This
switch position also enables a data link VOW key line by
activating relays in the Data Link Transmit Control Switch
Box located in the INS equipment rack aft of the copilot's
seat. This provides secure voice key capabilities whenever
the pilot or copilot key a microphone while the aircraft is
operated in the unmanned (no mission avionics operators)
configuration.
Change 3 3-3
