Sigtronics SPA-4S User manual

Sigtronics SPA-4S Installation Instructions
Specialists in “SOUND” Management
178 East Arrow Highway, San Dimas, CA 91773 ( 909 ) 305-9399
INTRODUCTION
ATTENTION INSTALLER: To assure a trouble free installation,
please read the entire instructions through once before
beginning.
SPA-4S SYSTEM SPECIFICATIONS
CONFIGURATION – The Sigtronics SPA-4S Intercom system is specically
designed for permanent, panel mounted installation in aircraft. The SPA-
4S provides voice activated (VOX) intercom and music input for up to four
headset positions in a small single chassis unit.
UPGRADE – A SPA-4S can upgrade an existing SPA-400 installation
requiring minimal re-wiring.
STEREO MUSIC INPUT – Music input accepts standard portable music
headphone or line level outputs. Automobile
Speaker level outputs can be adapted for use with SPA-4S systems.
COMPATIBILITY – Sigtronics SPA-4S intercoms have been designed to
operate with all standard general aviation aircraft radios and headsets.
SIZE: Panel – 1” x 2½”. Chassis – 1” high x 2½” wide x 4” deep.
Can be mounted either horizontally or vertically in the aircraft panel.
WEIGHT: 5.5 ounces (SPA-4S intercom unit with panel and knobs). Jacks
and wiring harness weigh 7.0 ounces
INPUT POWER: 11 VDC through 32 VDC. Maximum current drain 0.11
Amps
DISTORTION: Less than 1% total harmonic distortion.
WARRANTY: SPA-4S intercoms are constructed of high quality
components and carry a ve year parts and labor warranty.
HARDWARE SUPPLIED
Besides the intercom unit and instructions, each SPA-4S system comes
with the following hardware:
Headphone Output Jacks - Accept standard 0.250” aircraft
stereo headphone plugs. ......................................................................................... 4
Microphone Input Jacks - Accept standard 0.206” aircraft
microphone plugs. (U93 plug compatible jacks can be used in
place of the jacks provided – monaural installations only). ....................... 4
Mic Jack Insulating Washers, Flat .......................................................................... 4
Mic Jack Insulating Washers, Shoulder ............................................................... 4
Intercom Panel - lettered on both sides. ........................................................... 1
Intercom Control Knobs ........................................................................................... 2
Mounting Screws 4-40 x 1/2 ................................................................................... 2
Drill Template - Adhesive backed hole size pattern for
drilling aircraft panel. ................................................................................................ 1
Intercom / Aircraft Interface Cable (4 feet long) ............................................. 1
Headphone / Music Interface Cable (4 feet long) .......................................... 1
Stereo music input jack 3.5mm ............................................................................. 1
MUSIC MUTE OPTIONS
FACTORY DEFAULT - PARTIAL MUSIC MUTE DURING ICS - When
listening to music and someone speaks on the intercom the default
factory operation is to partially mute the music so you can hear the
conversation. The SPA-4S intercoms have one additional option that can
be enabled if desired. This option is enabled with the intercom removed
from the aircraft.
FULL MUSIC MUTE DURING ICS OPTION - The music can be completely
muted during intercom conversations. To enable this option, small jumper
wires are installed on the solder side of the circuit board.
HIGH NOISE VERSION
Model SPA-4SN – The “N” version of the SPA-4S has all the above features
but is specically congured for very high noise environments such as
open cockpit aircraft, warbirds, and ultralights. In addition to special
circuitry that improves intercom performance in high noise aircraft, the
SPA-4SN has a Push-to-intercom mode for applications where voice
activated (VOX) intercom operation is not desired.
CHASSIS INSTALLATION
To upgrade an existing SPA-400 installation to a SPA-4S skip to the
“UPGRADING A SPA INSTALLATION TO A SPA-4S” section on page 2. For a
completely new intercom installation, continue below.
Unit Placement
The SPA-4S unit has been designed to mount either horizontally or
vertically in your aircraft panel. The location selected for the SPA-4S unit
requires a minimum front panel area of 2½” by 1”. Depth required behind
panel is 4” plus cable access.
CAUTION: Move the aircraft ight controls through the limits of travel
while observing the selected area and making sure that the rear of the
intercom and cable will not interfere with any aircraft control components.
Panel Preparation
1. Position the adhesive drill template on the aircraft panel in the selected
area.
2. Center punch each hole at the cross lines. (Five holes are in a straight
line and equally spaced 0.4” apart)
3. Drill ¹⁄₈” pilot holes in all ve places.
4. Enlarge holes to ¼” and ³⁄₈” per the template.
WARNING: This product can expose you to chemicals including
Polyvinyl Chloride, which is known to the State of California to
cause cancer, and Lead, which is known to the State of California
to cause birth defects or other reproductive harm. For more
information go to www.P65Warnings.ca.gov.

SHOULDER
WASHER
FLAT
INSULATED
WASHER
FLAT
METAL
WASHER
NUT
AIRCRAFT
PANEL
RING
BARREL
TIP
Figure 5
TIP
(RIGHT)
RING
(LEFT)
BARREL
(COMMON)
AIRCRAFT PANEL
NUT
Figure 3
Microphone Jack
RIGHT
LEFT
STEREO
+
-
+
-
+-
+-
RC
RC
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
Figure 2
4–40 SCREWS SWITCH
NUT
KNOB
KNOB
AIRCRAFT PANEL
INTERCOM PANEL
DO NOT
REMOVE
THESE
NUTS
INTERCOM CHASSIS
MOD. ADJ.
MOUNTING CHASSIS (See Figure 2)
1. Remove the knobs from the Volume and Squelch controls using a 0.050”
Allen wrench. Remove the nut from the ON/OFF switch. NOTE: DO NOT
REMOVE the nuts from the Volume and Squelch controls.
2. Insert the SPA-4S unit from the rear of the aircraft panel with the
appropriate UP arrow for horizontal or vertical installation.
3. Install the printed SPA-4S panel and lightly thread the two 4-40 screws
through the holes in intercom panel. The nuts on the Volume and Squelch
controls will t inside the ³⁄₈” diameter holes.
4. Tighten the two screws and switch nut.
5. Install the knobs on the Volume (VOL) and Squelch (SQ) control shafts
and tighten the Allen screws.
MOUNTING HEADPHONE AND MICROPHONE JACKS (See Figure 3)
1. Locate the mounting areas. (One mic and one headphone jack required
for each headset). Again, make sure that the jacks will not interfere with
any aircraft control components. (Note that the jack contacts will expand
when a plug is inserted into the jack and must have clearance to prevent
shorting.)
2. Drill ³⁄₈” diameter holes for headphone jacks and install.
3. Drill ½” diameter holes for the mic jacks and install with the insulating
washers supplied. (See Figure 3).
Note: If the aircraft already has pilot headset jacks, the location can be used
for intercom with the following changes. The mic jack must be re-wired as
follows:
1. Remove any existing wires from the tip, ring, and barrel connections.
2. Connect the intercom white/black wire to the ring terminal.
3. Connect one end of a ground wire to the barrel terminal of the mic jack
and connect the other end to Intercom Central ground Point “A”.
4. Install insulating washers as necessary if the barrel of the mic jack is
mounted in metal. For the headphone jack, replace the mono headphone
jack with the stereo headphone jack. Connect the green wire (P2 pin 1)
to the tip connection. Connect the white/green wire (P2 pin 2) to the
ring connection.
WIRING INSTRUCTIONS
Connections should be made as shown in Figure 4 and indicated in Tables
1 and 2. Read also the referenced notes below. If longer wire lengths are
required, use a good quality multi stranded hook-up wire - 22 gauge or
larger. Although not necessary, shielded audio wire can be used if desired.
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 signicantly when switching the ON/OFF switch
a minor adjustment to the radio receive potentiometer will x this. See
“INSTALLATION CHECK-OUT AND ADJUSTMENTS” section on page 4.
2. Connect all intercom mic jack grounds to a single aircraft chassis ground
point - Intercom Central ground Point “A” - as shown in Figure 4. (Use the
black washers supplied to insulate the intercom mic jacks from aircraft
chassis ground). Note this intercom 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 Central Ground
Point “A” on their own individual ground wire. Similarly, both intercom
ground wires (J1 pin 4) and the push-to-transmit switch grounds must
also be connected back to Intercom 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 require 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
¼” 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-4S system. A Floating
Ground Adapter or a four wire to three wire converter will have to be used
between the Stereo and the SPA-4S music input. Figure 6 shows such an
adapter and how it is wired into the SPA-4S.
6. The Sigtronics SPA-4S system 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-4S 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.
7. The Violet wire (J1 pin 12) is provided on SPA-4SN models only for an
optional Push-to-intercom function. For wiring and additional instructions
on the SPA-4SN see the “SPA-4SN PUSH-TO-INTERCOM INSTRUCTIONS”
section on page 4. Make sure any unused wires are properly insulated
and kept from shorting to any other wires or aircraft ground. Skip to the
“INSTALLATION CHECK OUT AND ADJUSTMENT” section on page 4.
UPGRADING A SPA INSTALLATION TO A SPA-4S
Chassis Mounting
The SPA-4S is specically designed to easily replace a SPA-400. The intercoms
are exactly the same dimensions (1” x 2½” x 4”). Five mounting holes are
exactly in the same positions. To upgrade, rst remove the SPA-400 unit
Page 2 SigtronicS SPA-4S PAnel Mount intercoMS www.SigtronicS.coM

INTERCOM
CIRCUIT
BREAKER
(1 AMP)
12345
AIRCRAFT RADIO
Stereo Intercom
VOL
SQ ON
SPA-4S
POINT
AIRCRAFT / INTERCOM
INTERFACE AREA
J2 (4) WHITE / BROWN
J2 (5) BLACK
J2 (6) WHITE / VIOLET
J1 (9) TAN
J1 (8) TAN
J2 (1) GREEN
J2 (2) WHITE / GREEN
TO AIRCRAFT
POWER BUSS
12/28 VDC (INTERCOM
CENTRAL
GROUND
POINT)
A
J1 (2) WHITE / RED
J1 (3) BLUE
J1 (6) BROWN
J1 (10) WHITE / BLUE
J1 (5) WHITE
J1 (4) BLACK J1 (7) RED
TO
TO
AIRCRAFT
HEADPHONE
JACK
AIRCRAFT
HAND MIC
JACK
PILOT
PTT SWITCH
CO-PILOT
PTT SWITCH
A
A
P2
J2
MUSIC
INPUT JACK
P1
J1
J1 (1) WHITE / BLACK
J1 (11) WHITE / ORANGE
SPA-4S
INTERCOM
HEADPHONE AUDIO
MIC AUDIO
RADIO MIC KEY
PASSENGER 2
HEADPHONE
JACK
TIP RING
BARREL
TIP
RING
MIC
JACK
BARREL
A
TO
CO-PILOT
HEADPHONE
JACK
MIC
JACK
BARREL
TIP RING
BARREL
TIP
RING
A
TO
PILOT
HEADPHONE
JACK
MIC
JACK
BARREL
TIP RING
BARREL
RING TIP
TO A
PASSENGER 1
HEADPHONE
JACK
MIC
JACK
BARREL
TIP
RING RING
BARREL
A
TO
TIP
BARREL
TIPRING
TIP
TIPRING
AIRCRAFT CHASSIS GROUND.
2.)
NOTES
1.) IF PILOT PTT SWITCH IS CONNECTED
TO THE AIRCRAFT HAND MIC JACK,
IT MUST BE DISCONNECTED AND
CONNECTED TO THE WHITE/RED
WIRE AS SHOWN.
SPA-4S INSTALLATION DRAWING
PORTABLE STEREO
HEADPHONE
RADIO RECEIVE
ADJUST
Figure 4
from the aircraft panel. This is done by unscrewing the two Phillips head
screws and the nut on the ON/OFF switch. Remove the printed SPA-400
panel. Pull the SPA-400 unit out and unplug the white connector from the
wiring harness. Finally mount the SPA-4S chassis (see Figure 2 on page 2):
1. Remove the knobs from the Volume and Squelch controls using a 0.050”
Allen wrench. Remove the nut form the ON/OFF switch. NOTE: DO NOT
REMOVE the nuts from the Volume or Squelch (VOL/ SQ) controls.
2. Insert the SPA-4S unit from the rear of the aircraft panel with the
appropriate arrow on the unit chassis pointing upwards.
3. Install the printed SPA-4S panel and lightly thread the two 4-40 screws
through the holes in intercom panel. The nuts on the Volume/Squelch
controls should t inside the aircraft panel holes.
4. Tighten the two screws
5. Put the knobs on the Volume and Squelch control shafts, tighten the Allen
screws, and switch nut.
Wiring Change
The wiring changes to an existing SPA installation are as follows. Re-wire
the pilot, co-pilot, and passenger(s) headphone lines. You will not need
the 4-foot intercom / aircraft interface cable (12 pin) that comes with the
SPA-4S system. You will use the SPA harness already in the aircraft and the
4-foot headphone / music interface cable (6 pin). In a SPA-400 installation,
the tip terminals of the pilot, co-pilot, and passenger headphone jacks are
wired to the blue wire (pin 3). They need to be disconnected from there,
the mono headphone jacks need to be replaced with the supplied stereo
headphone jacks and connected to their respective pins on the headphone
/ music interface harness. (See Figure 4 on page 3) Make sure that the blue
wire (pin 3) is still connected to the tip of the radio headphone line. Wire
the music input as shown in Figure 4 on page 3.
MONO MUSIC
Rewire the headphone jacks as shown in the installation wiring diagram.
For mono music you can use the existing jacks. Connect the green P2(1) and
the white/green P2(2) to tip terminal of the phone jacks.
NOTE: Make sure that the blue headphone wire from the original SPA-400
installation is not connected to the headphone jacks tip connection and is
connected to the aircraft audio panel or radio as shown in gure 4 on page 3.
TABLE 1 - P1/J1 - See Wiring Instructions
PIN WIRE COLOR FUNCTION CONNECT TO
1White/Black Pilot Mic Input Ring Terminal of Pilot Mic Jack
2White/Red Pilot Transmit Switch
Input
Pilot Transmit Switch (PTT) (Switch
to Ground to Transmit)
3Blue *1 Radio Headphone Input Radio Headphone Output
4Black *2 Intercom Central
Grounding Point“A” Aircraft Chassis Ground
5White Radio Transmit Key
Output
Tip Terminal of Aircraft Hand Mic
Jack, or Key Input of Aircraft Radio
or Audio Panel
6Brown Transmit Mic Audio
Output
Ring Terminal of Aircraft Hand Mic
Jack or Mic Input of Aircraft Radio
or Audio Panel
7Red *3 12 through 28 VDC Power
Input Intercom Circuit Breaker
8Tan *4 Passenger #1 Mic Input Ring Terminal of Passenger #1
Intercom Mic Jack
9Tan *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
1Green *6 Intercom Right
Headphone Output Tip Terminal of Headphone Jack
2White/Green *6 Intercom Left
Headphone Output Ring Terminal of Headphone Jack
3NC None No Connection
4White/Brown *2 Music Input Left Channel Left Music Source Headphone or
Line output
5Black *5 Music Input Common Music Source Common Headphone
or Line Output
6White/Violet *5 Music Input Right Channel Right Music Source Headphone or
Line Output
www.SigtronicS.coM SigtronicS SPA-4S PAnel Mount intercoMS Page 3

(12) VIOLET
TO
TO
To SPA-4SN
J1 Pin 12
Push-To-Intercom Switches
( 1 Per Headset )
A
A
Figure 8
Figure 7
Sigtronics Corporation
178 East Arrow Highway
San Dimas, CA 91773
909) 305-9399
www.sigtronics.com
HOW TO SELECT MUSIC OPTION
To select full music mute during intercom, the unit must be removed from
the aircraft. This is done by rst removing the volume and squelch control
knobs with a 0.05 inch Allen wrench. Then remove the two mounting screws
and switch nut that holds the unit in the panel. The unit is now free for
removal from the aircraft after disconnecting the cables at the plugs.
To enable this option, modication to the bottom of the units’ circuit
board is required. CAUTION – a qualied technician should perform this
modication. First remove the three screws securing the bottom cover to
the case and carefully lift and remove the cover. Note that the circuit board
does not have to be removed from its case to complete the modications.
To select full mute during intercom solder the two small-insulated jumper
wires at the locations specied in Figure 7.
Replace the cover and secure it with the three screws as before. Install the
unit back into the panel and plug in the two cables.
SPA-4SN PUSH-TO-INTERCOM INSTRUCTIONS
Install a separate momentary switch at each headset position. Connect
per Figure 8. To use the push-to-intercom feature, turn the squelch control
on the intercom fully counter-clockwise. Then to activate, press the push-
to-intercom switch(s). Alternately, to use the intercom in voice activated
(VOX) mode set the intercom squelch as normal. See the separate SPA-4S
OPERATING INSTRUCTIONS sheet.
INSTALLATION CHECK-OUT AND ADJUSTMENTS
After the unit is installed, again check that the SPA-4S 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-4S unit installation,
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
¼” from the lips.
To assure that the aircraft radios, pilot’s headset, and PTT switch are
connected and functioning properly, switch the SPA-4S ON/OFF switch to
the “o” position. If applicable, set the aircraft audio panel to “Headphone”
position. Then turn on the aircraft radio(s) as usual, and verify that the pilot
can hear the radios and can transmit using his push-to-transmit switch and
headset. Aircraft radio(s) and audio panel should operate exactly as they
did before the SPA-4S system was installed. Aircraft radio reception should
also be heard in the co-pilot and passenger headsets. There should be no
intercom between headsets with the SPA-4S unit “o”. Next turn the SPA-4S
unit “on”. Set the SPA-4S volume control to mid-position. Set SPA-4S squelch
control fully clockwise. Verify that the Pilot and co-pilot can operate the
aircraft radio(s). As before, all headsets on the intercom will hear the aircraft
radio(s). Check that all headset positions can intercom.
Mic Output Adjust
It may be necessary at this time to adjust the SPA-4S unit mic output to
the aircraft radios. A small adjustable potentiometer is provided inside
the unit for this purpose. It is accessible through a hole in the side of the
SPA-4S chassis. It is marked “Mod. Adj.”, and can be adjusted with a small
blade screwdriver (see Figure 2). 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 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
event of low aircraft radio volume in the “ON” mode relative to “OFF” mode,
an appropriate adjustment can be made. Clockwise rotation increases the
input level to the SPA radio receive input. Counter-clockwise rotation
decreases input level. This adjustment sometimes needs to be made after
the initial installation of the intercom or if a new radio is installed that has a
low output impedance or low output power. The adjustment is best made
with all headsets plugged in. (The input is set full CCW which is unity gain for
500Ω radios). Note: Be sure to replace the sticker when you have completed
the adjustment.
You are now ready to check for proper wiring of the music source. First, make
sure squelch is o (full counter clockwise) and intercom is ON. Turn on the
music source and listen for music through pilot and co-pilot headsets, and
passenger headsets. There should be music.
If everything checks out, refer to the SPA-4S OPERATING INSTRUCTIONS
sheet for proper use and other operating modes of the Sigtronics SPA-4S
intercom system. If something does not work as described, carefully go over
the intercom wiring again. If something is still not right or you have any
questions regarding the installation and operation of the Sigtronics SPA-4S
intercom or any other Sigtronics product feel free to contact us directly or
E-mail us at [e-mail]. Technicians are available Monday though
Friday 8 am to 4:30 PM Pacic time.
See the separate SPA-4S OPERATING INSTRUCTIONS sheet for complete
operation information.
SPA-4S_REV-I_Installation.pdf 8-8-2023 PN 700115
FAA TSO: C50b ENV. CAT (DO-160) CFBBBX
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