PS Engineering PM2CREW - Manual (Page 6)

PS Engineering
PM2Crew Expansion module (11918)
200-004-0004 Page 2-3 Rev. 4, Sept. 2000
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.
2.4.2 Power Requirements
The PM2CREW was designed to work with the main intercom unit. No other power is required.
2.4.3 Interconnection with main unit
Interface between the PM2CREW and the main intercom is through a 5-wire shielded cable. Monaural
systems, such as the PM1000-series or PMA4000 require the left and right sides of the audio input be
combined. A 4-conductor cable can be used with these systems.
Function PM2CREW PM2000 PM1000 Series PMA4000
Expansion Power 1 17 15 17
Expansion Ground 14 1 2 3
Audio Input (rt.) 2 5
Audio Input (lt.) 15 18
16 4
Audio Output 3 4 3 5
2.4.4 Six and eight place units (11918P6 and 11918R6, 11918P8 and 11918R8)
The PM2CREW 6- and 8-place versions reconfigure the microphone input, converting mic grounds into
MIC high, and therefore are not interchangeable with a standard 4-place 11918 unit. Two extra headsets
are paralleled from the amplifiers.
2.4.5 Auxiliary Inputs
An entertainment device can be connected to the PM2CREW. Install a 1/8" music jack convenient to the
passengers to connect the stereo entertainment device into the system. A "Soft Mute" system is installed in
the PM2CREW that will mute the music during conversation on the local intercom. Radio traffic or
conversation on the main intercom will not mute the music.
A second, monaural input is provided for other purposes, such as public address cabin briefing, or
providing radio interface for cases where the intercom does not have radio on the expansion bus
(PM1000D for example).
NOTE:
The PMA4000 music input is present on the expansion output. If this is used, DO NOT connect the
entertainment input to the PM2CREW.
A soft mute inhibit switch (not included) can be installed between 11918 connector pins 12 and 24.
Closing this switch places the PM2CREW into Karoake mode.
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.