Specifications

SECTION III
MODEL 560 INSTRUMENTATION AND AVIONICS
HONEYWELL PRIMUS II REMOTE RADIO SYSTEM - AUDIO CONTROL UNIT
Two Honeywell Primus II digital audio control units (AV-850A) are supplied with the Honeywell Primus
II remote radio system. Digital transmission of audio from remote units to the audio panels differs from
conventional audio systems in that it requires one twisted pair of wires rather than many twisted pairs to
achieve the same performance.
The panels have three rows of combination audio ON/OFF switches and volume controls. The small
round knobs serve as audio on/off switches when pressed. When the switch is latched in, the audio for the
particular receiver it serves will be off. When pressed again, the switch will move outward turning the
audio on. When the audio is on, the knob of the switch may be used as a volume control. Turning it
clockwise will increase the volume; counter-clockwise will decrease it.
Two larger knobs on the lower part of the control panel serve as volume controls for the speaker and
headset respectively, of the pilot and copilot. These knobs are in series with the smaller individual volume
controls. This allows a volume selection to be made on the individual radio volume control, and then a final
overall selection to be made by means of the speaker or headphone control, resulting in a more flexible
individual control of all available audio signals.
A row of microphone selector buttons (push-push latching switches) is located across the top of the
control panel. These buttons connect the pilot's or copilot's microphone to the selected transmitter. The
receiver for the selected radio or interphone will also be selected regardless of the selection of the audio
on/off switches. For night operation, a light above the microphone selector button is illuminated.
The emergency COM (EMER) microphone switch, located at the upper right corner of the audio
panel, when depressed connects COM 1 transceiver directly to the aircraft microphone and headphone.
All electronic circuitry is eliminated and all other audio panel modes are disabled in this mode. NAV 2
audio will also be directed into the headset controlled by the panel on which EMER is activated, if NAV
AUDIO is selected on the CDU.
Figure 3-10. PRIMUS II - Audio Control Panel (Typical)
I 56OMB-01 Configuration AA 3-23