3
TABLE 1 - P1/J1 - See Wiring Instructions
PIN
WIRE COLOR FUNCTION
CONNECT TO
1
White/Black
Pilot Mic Input
Ring Terminal of Pilot Mic Jack
2
White/Red
Pilot Transmit Switch
Input
Pilot Transmit Switch (PTT)
(Switch to Ground to Transmit)
3
Blue *1 Radio Headphone Input Radio Headphone Output
4
Black *2
Intercom Central
Grounding Point “A”
Aircraft Chassis Ground
5
White
Radio Transmit Key
Output
Tip Terminal of Aircraft Hand Mic
Jack, or Key Input of Aircraft Radio
or Audio Panel
6
Brown
Transmit Mic Audio
Output
Ring Terminal of Aircraft Hand Mic
Jack or Mic Input of Aircraft Radio
or Audio Panel
7
Red *3
12 through 28 VDC
Power Input
Intercom Circuit Breaker
8
Tan *4 Passenger #1 Mic Input
Ring Terminal of Passenger #1
Intercom Mic Jack
9
Tan *4 Passenger #2 Mic Input
Ring Terminal of Passenger #2
Intercom Mic Jack
10
White/Blue
Co-Pilot Transmit Switch
Input
Co-Pilot Transmit Switch (PTT)
(Switch to Ground to Transmit)
11
White/Orange Co-Pilot Mic Input
Ring Terminal of Co-Pilot Mic Jack
12
Violet *7 ICS PTT
ICS PTT Switches
TABLE 2 - P2/J2 - See Wiring Instructions
PIN
WIRE COLOR FUNCTION
CONNECT TO
1
Green *6
Intercom Right
Headphone Output
Tip Terminal of Headphone Jack
2
White/Green
*6
Intercom Left Head-
phone Output
Ring Terminal of Headphone Jack
3
N/C None
No
Connection
4
White/Brown
*5
Music Input
Left Channel
Left Music Source
Headphone or Line output
5
Black *5
Music Input
Common
Music Source Common
Headphone or Line Output
6
White/Violet
*5
Music Input
Right Channel
Right Music Source
Headphone or Line Output
1. The blue wire from Pin 3 must be connected to the aircraft radio
headphone output - NOT the speaker output. NOTE – If aircraft
radio volume heard in the headsets changes significantly when
switching the ON/OFF switch a minor modification to the instal-
lation will fix this. Just install a small ¼ watt resistor inline with
the blue wire. Select a value between 220 and 560 ohms for
best results.
2. Connect all intercom mic jack grounds to a single aircraft chas-
sis ground point - Intercom Central ground Point “A” - as shown
in Figure 4. (Use the black washers supplied to insulate the in-
tercom mic jacks from aircraft chassis ground). Note this inter-
com central grounding point is used to eliminate any unwanted
electrical noises, such as alternator whine or strobe noise, from
being induced into the intercom system through the grounds.
All intercom mic jack barrels must be insulated from ground
where they are mounted and connected back to Intercom Cen-
tral Ground Point “A” on their own individual ground wire. Simi-
larly, both intercom ground wires (J1 pin 4) and the push-to-
transmit switch grounds must also be connected back to Inter-
com Central Ground Point “A”. It is not necessary, however, to
connect the headphone jack barrels to Intercom Central
Ground Point “A”. They can either be grounded where they are
mounted or some place nearby.
3. The red wire may be connected to either 12V (14V) or 24V
(28V) power source. No switching or adjustments are required
to operate from either source.
4. Tan wires (J1 pins 8, 9) are only used on installations that re-
quire the two rear intercom positions.
5. The SPA-4S system provides a stereo music input. This music
input accepts portable music Headphone or Line level music
sources. The wiring diagram shows how to wire the SPA-4S for
use with a portable stereo music source. A small stereo input
jack is supplied for this purpose. Connect the White/Brown,
White/Violet, and Black wires to one jack as shown in Figure 4.
Identify the jack terminals using Figure 5. Drill a 1/4-inch hole
for the jack and mount on the aircraft panel. To use, connect an
adapter cable between the music input jack and the output of
FIGURE 4
