PS Engineering
PCD7100 Series Intercom System with Integral Music System
Installation and Operator’s Manual
2.3.4 Connector
Assembly
The unit connector mates directly with the circuit boards in the PCD7100. The connector is a Molex crimp-
type, and requires the use of a Molex hand crimp tool, EDP P/N 11-01-0203, CR6115B (or equiv.). The
connector is mounted to the unit tray with #4-40 screws, from the inside of the tray. Ensure that proper
strain relief and chafing precautions are made during wiring and installation.
2.4
Cable Harness Wiring
Referring to the appropriate Appendix, assemble a wiring harness as required for the installation. All wires
must be MIL-SPEC in accordance with current regulations. Two- and three-conductor shielded wire must
be used where indicated, and be MIL-C-27500 or equivalent specification. Proper stripping, shielding and
soldering technique must be used at all times. It is imperative that correct wire be used.
Refer to FAA Advisory Circular 43.13-2A for more information. Failure to use correct techniques may
result in improper operation, electrical noise or unit failure. Damage caused by improper installation will
void the PS Engineering warranty. PS Engineering can provide a custom made harness, visit
www.ps-
engineering.com
for more information.
2.4.1 Noise
Due to the variety and the high power of radio equipment often found in today's general aviation aircraft,
there is a potential for both radiated and conducted noise interference.
The PCD7100 power supply is specifically designed to reduce conducted electrical noise on the aircraft
power bus by at least 50dB. Although this is a large amount of attenuation, it may not eliminate all noise,
particularly if the amplitude of noise is very high. There must be at least 12 VDC present at the connector
pin 21, of the PCD7100 for the power supply to work in its designed regulation. Otherwise, it cannot ade-
quately attenuate power line noise. Shielding can reduce or prevent radiated noise (i.e., beacon, electric
gyros, switching power supplies, etc.) However, installation combinations can occur where interference is
possible. The PCD7100 was designed in a RFI hardened chassis and has internal Electromagnetic Interfer-
ence (EMI) filters on all inputs and outputs.
Ground loop noise occurs when there are two or more ground paths for the same signal (i.e., airframe and
ground return wire). Large cyclic loads such as strobes, inverters, etc., can inject noise signals onto the
airframe that are detected by the audio system. Follow the wiring diagram very carefully to help ensure a
minimum of ground loop potential. Use only Mil Spec shielded wires (MIL-C-275000, or better).
Radiated signals can be a factor when low level microphone signals are "bundled" with current carrying
power wires. Keep these cables physically separated. It is very important that you use insulated washers to
isolate the ground return path from the airframe to
all
headphone and microphone jacks.
2.4.2 Power
The PCD7100-Series units are compatible with both 14 and 28 Volt DC systems. A three- (3) Amp PULL-
TYPE circuit breaker is required for p/n 11950, 11951, or two (2) Amp PULL-TYPE breaker for p/n
11951, or 11952. Power and ground wires must be a twisted #18 AWG pair. Connect airframe power
ground to Pin 22 only.
2.4.3 Communications Push-to-Talk
An important part of the standard intercom installation (11950, 11951) is the PTT (Push-To-Talk) switches
that allow the use of your aircraft communications radio for transmissions. There are three typical configu-
rations that can be used. Select the case that best fits the installation. Only the person who presses their
PTT switch will be heard over the radio. If the pilot and copilot both use the PTT, the only pilot position
has access to the radio. The pilot position will have PTT control regardless of the mic selector switch or
copilot PTT when the PCD7100 is in the F
AIL
-
SAFE
mode.
200-971-0005
Page 2-2
Rev. 5, Dec. 2002
