Sigtronics SPA-4Si - Manual (Page 4)

RIGHT
LEFT
STEREO
+
-
+
-
+ -
+ -
R C
R C
C – 220 MFD, 25 VOLT CAPACITOR
R – 100 OHM, 5 WATT RESISTOR
NO CONNECTION
J2 (6) WHITE / VIOLET
J2 (4) WHITE / BROWN
J2 (5) BLACK
To SPA-4S
Figure 6
To SPA-4Si
BARREL
TIP
RING
(COMMON)
(LEFT)
(RIGHT)
AIRCRAFT PANEL
NUT
Figure 5
page 4
5. Each SPA-4Si unit 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-4Si 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 the portable stereo.
Suitable cables are available at your
local stereo or electronics store as
well as from Sigtronics. Speaker level
output car stereo music sources can
also be used with the SPA-4Si units. A Floating Ground Adapter or a four
wire to three wire converter will have to be used between the Stereo and
the SPA-4Si music input (either separate or single inputs). Figure 6 shows
such an adapter and how it is wired into the SPA-4Si.
6. If using only a single portable music source there are two different meth-
ods that can be used. For a system with two SPA-4Si units the easiest way
is to wire just like the wiring drawing and use a mini-jack “Y” or splitter
(available at your local stereo or electronics store). Use the splitter and
dual cables to go from the music source into both SPA-4Si input jacks.
The second way is to use just one of the supplied music input jacks and
connect all inputs to it. Do this by connecting all (J2) White/Violet wires
to the TIP terminal, all (J2) White/Brown wires to the RING, and all (J2)
Black wires to the BARREL. This method will work for systems with two
or more SPA-4Si units.
7. The Sigtronics Dual Bus Kit can be installed as shown for use with Stereo
headsets. Alternatively, monaural general aviation type headsets can
be used. To use monaural headsets follow the installation instructions
as normal except for the wiring of the stereo headphone jacks. Use the
stereo headphone jacks supplied with the Sigtronics SPA-4Si units but
leave the “RING” connections open. Instead connect both headphone
wires to the “TIP” of the respective jacks. Connect both the WHITE/GREEN
and GREEN on to the TIP of the headphone jack.
INSTALLATION CHECK-OUT AND ADJUSTMENTS
After the units are installed, again check that the SPA-4Si unit chassis, jacks,
and wiring harness are clear of all aircraft operating controls and cause no
interference with them.
Next, to check out the SPA-4Si unit installations, plug in all the headset
mic and phone plugs into the respective intercom jacks. Put on the pilot’s
headset and position the boom mic close to the mouth. Voice clarity is best
when the mic is at one side of the mouth and 1/4” from the lips.
To assure that the aircraft radios, pilot’s headsets, and PTT switches are
connected and functioning properly, switch all SPA-4Si ON/OFF switches
to the “OFF” position. Set both audio panels to “Headphone” position. Then
turn on the aircraft radios as usual, and verify that the pilot and co-pilot can
hear the radios and can transmit using their respective push-to-transmit
switches and headsets. Aircraft radios and both audio panels should operate
exactly as they did before the SPA-4Si units were installed. Aircraft radio
reception should also be heard in the passenger headsets if used. There
should be no intercom between headsets with the SPA-4Si units “OFF”.
Next turn both SPA-4Si units “ON”. Set the SPA-4Si volume controls to mid-
position. Set SPA-4Si squelch controls fully clockwise. Verify that all headset
positions, including the passenger positions if used, can intercom to each
other.
MIC OUTPUT ADJUST
It may be necessary at this time to adjust the SPA-4Si units mic output to
the aircraft radios. A small adjustable potentiometer is provided inside
the units for this purpose. It is accessible through a hole in the side of the
SPA-4Si chassis. It is marked “Mod. Adj.”, and can be adjusted with a small
blade screwdriver. In the event of over-modulation (garbled) or reports
of weak transmissions over the aircraft radio, an appropriate adjustment
can be made. Clockwise rotation increases the output level to the aircraft
radio mic input. Counter-clockwise rotation decreases modulation level.
This adjustment sometimes needs to be made after the initial installation
of the intercom or if a new radio is installed. (The output is set for unity
gain at Sigtronics).
RADIO RECEIVE ADJUST
It may also be necessary to adjust the unit’s radio receive input from the
aircraft radio. A small adjustable potentiometer is provided inside the unit
for this purpose. It is accessible under a sticker on top of the chassis box
(see Figure 4), and can be adjusted with a small blade screwdriver. In the
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
Radio Transmit Key Output Tip Terminal of Aircraft Hand Mic
Jack, or Key Input of Aircraft Radio
or Audio Panel
3 Blue *1 Radio Headphone Input Radio Headphone Output
4 Black *2
Intercom Central
Grounding Point “A” Aircraft Chassis Ground
5 N/C — —
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 #2 Mic Input Ring Terminal of Passenger #2
Intercom Mic Jack
9 Tan *4
Passenger #3 Mic Input Ring Terminal of Passenger #3
Intercom Mic Jack
10 White/Yellow Music Mute Link White/Yellow of any Other Units
11 White/Orange *4
Passenger #1 Mic Input Ring Terminal of Passenger #1
Intercom Mic Jack
12 Yellow Bidirectional Intercom Link Yellow of any Other Units
TABLE 2 - P2/J2 - See Wiring Instructions
PIN WIRE COLOR FUNCTION CONNECT TO
1 G r e e n * 7
Intercom Right
Headphone Output Tip Terminal of Headphone Jack
2 White/Green *7
Intercom Left Head-
phone Output Ring Terminal of Headphone Jack
3 N/C — —
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