Bendix/King
KMA 28B Audio Selector Panel and Intercom System
Installation and Operator’s Manual
D201106000060
Page 2-5
June 2011
NOTE
Unauthorized use of unapproved cellular telephone devices in aircraft is subject to FCC enforcement ac-
tion, which may include a $10,000 fine per incident.
FCC Regulation 47 CFR § 22.925
Prohibition on airborne operation of cellular telephones
.
Cellular telephones installed in or carried aboard airplanes, balloons or any other type of aircraft must not
be operated while such aircraft are airborne (not touching the ground). When any aircraft leaves the
ground, all cellular telephones on board that aircraft must be turned off.
PS Engineering, Inc. does not endorse using unapproved cellular telephone equipment in flight, and takes
no responsibility for the user’s action.
2.4.6
Transmit Interlock
Some communications transceivers use a transmit-interlock system. To utilize the Split Mode feature
fully, this function must be disabled. Consult that manufacturer's installation manual.
2.4.7
"Swap" Mode
When a momentary, normally open, push-button switch is connected between pin 10 on the top connector
and aircraft ground, the user can switch between Com 1 and 2 by depressing this switch without having to
turn the mic selector switch. This yoke-mounted switch eliminates the need to remove your hands from
the yoke to change transceivers. The transfer of TX indication from Com 1 to Com 2 shows that the swap
has been initiated; there is no dedicated swap indicator.
2.4.8
Backlighting
The KMA 28B has an automatic dimming of the pushbutton annunciator LEDs and marker lamps con-
trolled by a photocell. Control of the unit backlighting is through the aircraft avionics dimmer. Connect
the dimmer control line to J1 pin D for 14 volt systems, and to J1 pin F for 28 volt systems. Pin E is light
ground.
If an external dimmer control is
not
used, a constant low level back light illumination can be established
for nighttime viewing. Pin D or F (depending on system voltage) must be tied to power (J1, pin 20) for the
back lighting system to work. The photocell mounted in the unit face will automatically adjust the inten-
sity of the push-button annunciator LEDs.
2.4.9
Unswitched inputs
J1, pins T, 17, U and X are unswitched, unmuted inputs. These inputs are presented to the pilot and copi-
lot regardless of the audio configuration, and will always mute the entertainment inputs. These 510Ω in-
puts can be used for altimeter DH audio, GPS waypoint audio, autopilot disconnect tones, or any other
critical audio signal... Pin T is provided to the pilot’s headset even when the unit is off, or in fail-safe
mode. NOTE: Inputs 1, 2 and 4 are fixed (1:1), and any audio level adjustments must be made at the input
source. Input 3 (Bottom Connector pin U) has adjustable attenuation.
2.4.10 PA Mute (J1, Pin 18)
Pin 18 of J1 is a TTL logic output that is pulled low during PTT operation. This serves as an input to ex-
ternal public address system to prevent feedback during transmissions.
2.4.11 Public Address Function (J2, Pin 18)
By connecting the top connector (J2), Pin 18 to ground, the pilot’s microphone audio is placed on the
cabin speaker output. When the pilot’s PTT is activated, his voice is heard over the speaker. The copilot
can continue to use the selected com.
We recommend installing a toggle switch to connect the cabin speaker output (pin W, bottom connector)
to a rear or public address speaker instead of the cockpit speaker close to the pilot. This will prevent feed-
back.
