PS Engineering PM1000II 11906 - Manual (Page 4)

May 2010 Page 4 200-124-0100 PM1000II Specialty Intercom Manual Page 4 May 2010
To connect intercom into the aircraft audio system,
parallel the appropriate set of cables from the intercom
to the Auxiliary Aircraft Radio Headset Jacks. Finally,
install new headset jacks into the aircraft and connect
them directly to the appropriate pins of the PM1000II.
See the wiring diagram for all details of the wire
harness interconnects.
2.2.1 Electrical Noise Issues
WARNING: You must use separate shielded
cables for the microphone and headphone jacks.
Combining these two wires WILL cause loud
oscillations and degrade the intercom function. The
oscillation is caused by the cross-coupling between the
large headphone signal and the small microphone
signal. The resulting feedback is a high-pitched squeal
that varies with the volume controls.
Due to the variety of the radio equipment found in
today's general aviation aircraft, there is the potential of
both radiated and conducted noise interference. The
PM1000II has a specially designed power supply to
reduce conducted electrical noise on the power bus of
the aircraft by at least 50dB. Although this is a very
large amount of attenuation, it does not eliminate all
noise when the amount is excessive. There must be at
least 12 Volts DC present at the PM1000II for the
power supply to work within its designed regulation.
Otherwise, it will not be able to attenuate noise
properly.
Shielding can protect the system from radiated
noise (rotating beacon, electric gyros, switching power
supplies, etc.). However, installation combinations can
occur where minor interference is possible. The
PM1000II was designed in an interference -protected
chassis and has internal filter capacitors on all input
lines.
Ground loop noise occurs when there are two
different return paths for the same signal, such as
airframe and ground return wire. Large cyclic loads
such as strobes, inverters, etc., can inject audible
signals onto the airframe return path. Follow the wiring
diagram very carefully to help insure a minimum of
ground loop potential. Radiated signals can be a factor
when low level mic signals are bundled with current
carrying power wires. Keep these cables separated.
Insulating washers are required on all mic and
headphone jacks to isolate them from aircraft ground.
The use of a conductor instead of a shield for ground
return eliminates these ground loop paths.
2.2.2 Power Requirements
The PM1000II was designed to work with either
12 or 28 volt DC negative ground systems. The
PM1000II must be externally protected with a one
ampere (1A) circuit breaker or fuse.
2.2.4 IRS Playback wiring
PM1000II part number 11906 and 11908 have an
internal recorder that stores recent incoming radio
messages. A 3.5 mm jack is provided on the rear of the
intercom unit to interface this function. Install a
momentary, normally open (NO), switch in a location
convenient to the pilot, and wire to the 3.5 mm plug
(included) across the tip and sleeve contacts. Closing
this switch will activate the playback. A low-current
rated switch is recommended.
2.2.3 Entertainment Input
Entertainment devices can be connected to the
PM1000II. Install the 1/8" jack convenient the pilot to
connect the entertainment device into the system. A
"Soft Mute" system is installed in the PM1000II that
will mute the music during intercom or radio activity.
Since the PM1000II is mono, and music jack is
stereo, it may be desirable to combine left and right
input channels at the jack, for connection to the music
input. Some devices may require a 10 Ώ resistor in
series with the left and right channels to isolate the
output amplifiers
The PM1000II w/Crew, 11908 has two (2)
entertainment inputs. In the ALL or ISO modes, Music
#1 is heard by everyone (except by the pilot in ISO
mode). In the CREW mode, pilot and copilot will hear
Music #1 while the passengers will hear entertainment
#2.
WARNING: Local oscillators and other internal
signals from CD or radio equipment can cause
undesired interference with VHF navigation and
communication equipment. Before takeoff, operate the
entertainment device to determine if there is any
adverse effect on aircraft systems. If any unusual
operation is noted in flight, immediately switch the
entertainment device off.
2.3 Post installation checkout
After wiring is complete, verify power is ONLY
on pin 14 of the connector, and airframe ground on pin
1. Failure to do so will cause internal damage and
void the warranty.
1. Apply power to the aircraft and avionics.
2. Plug headsets into the pilot, copilot and
passenger positions.
3. Verify that the pilot can transmit and receive
with the PM1000II in the OFF position (pilot
volume knob fully counterclockwise).
4. Rotate the pilot volume clockwise, about half
way. Verify that the Pwr/Xmt light comes on,
and shows green. If the LED is red, stop testing
and
trouble-shoot the microphone PTT
installation.
5. Verify that the pilot can transmit and receive on
the com transceivers.
6. Verify that the LED in the intercom changes
from green to red when a microphone is keyed.
7. Verify proper intercom operation for pilot,
copilot and passengers. For more information,
consult Section III.
8. Verify proper transmit and receive operation on
the copilot position, noting that the copilot PTT
switch allows proper transmission on the selected
transceiver.
9. Verify Intercom operation in the ALL, ISO and
CREW (if equipped) modes.
10. Verify that the intercom system does not
adversely affect any other aircraft system by
systematically switching the unit on and off,
while monitoring the other avionics and
electrical equipment on the aircraft.
11. Recorder Check Out Tune a communications
radio to an active 2-way channel, (not AWOS or
ATIS). Listen for a radio transmission. When it
is concluded, press the “Playback” button and
verify that the last message plays in the pilot
headset.
Section III OPERATION
With the installation complete, turn the PM1000II
on by rotating pilot's volume control. This also
engages the automatic fail-safe system. The pilot's
volume control does not control the volume of the
aircraft radio, allowing an additional degree of aircraft
radio listening flexibility.
3.1 Adjusting the Volume
The pilot's volume control knob adjusts the
loudness of the intercom and music for the pilot's
headset only. It has no effect on aircraft radio volume
level. The copilot's volume control adjusts the volume
for the copilot and passengers (11906).
In the 11908 (crew) units, the volume level for
both passengers can be adjusted by a screwdriver
adjusted potentiometer located on the left hand side of
the intercom as viewed from the front. It is possible to
adjust the overall output volume to the passenger
headsets by changing this potentiometer. Rotating the
potentiometer
counterclockwise increases the
passenger volume.
3.2 Squelch Control
The PM1000II provides individual VOX circuits
for the pilot and copilot. The ability to adjust the trip
level of these VOX circuits (squelch control) allows
the use of dissimilar headsets without the frustration of
clipping the first syllables. The PM1000II has three
squelch circuits, one for the pilot, copilot, and one for
the passengers. With individual VOX circuits,
background noise is dramatically reduced.
With the engine running, set the squelch control
knob by slowly rotating the squelch control knob
clockwise until you no longer hear the background
noise in the earphones. When the microphone is
positioned properly near the lips, normal speech levels
should open the channel. When you have stopped
talking, there is a delay of about one second before the
Note: Use the low level (or line) output from any music device to connect to
the PM1000II. Maximum input level is 2 V peak-to-peak.
DO NOT USE SPEAKER OUTPUT.
These levels will cause internal damage.
PM1000II, p/n 11906
PM1000II with crew, p/n 11908