Sigtronics SCI-S4 User manual

Sigtronics SCI-S4 / SCI-S6 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.
SCI-S4 / SCI-S6 SYSTEM SPECIFICATIONS
CONFIGURATION - The Sigtronics SCI-S Intercom systems are specically
designed for permanent, panel mounted installation in aircraft. Up to
four-position intercom is provided with the model SCI-S4. Model SCI-S6
handles up to six positions. “H” Model units for use in high noise aircraft.
UPGRADE - An SCI-S4 or SCI-S6 can replace an existing SPA-400, SPA-
600, ST-400, or ST-600 installation. This requires minor mounting hole
changes and minimal re-wiring.
DUAL STEREO MUSIC INPUTS - Both Crew and Passengers music inputs
accept standard headphone (Walkman) or line level inputs. Automobile
Speaker level outputs can be adapted for use with the SCI-S systems.
COMPATIBILITY – Sigtronics SCI-S 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 6” deep. Can be
mounted either horizontally or vertically in the aircraft panel.
WEIGHT: 7.3 ounces (SCI-S4 intercom unit with panel and knobs). Jacks
and wiring harness weigh 8.9 ounces. 7.5 ounces (SCI-S6 intercom unit
with panel and knobs). Jacks and wiring harness weigh 10.9 ounces.
INPUT POWER: 11VDC through 32VDC. Maximum current drain 0.2
Amp (SCI-S6)
DISTORTION: Less than 1% total harmonic distortion.
WARRANTY: The SCI-S units are constructed of high quality components
and carry a ve year parts and labor warranty.
FAA TSO: C-50c
ENVIRONMENTAL: DO -160D
Environmental Catagory:
A1D1XCAAS2MXXXXXXZBBBBXXXXXXXXXXX
Hardware Supplied
Besides the intercom unit and instructions, each SCI-S system comes
with the following hardware:
SCI-S4 SCI-S6
Headphone Output Jacks - Accept standard
0.250” aircraft stereo headphone plugs 4 6
Microphone Input Jacks - Accept standard
0.206” aircraft microphone plugs. (U93 plug
compatible jacks can be used in place of the
jacks provided - mono installations only)
4 6
Mic Jack Insulating Washers, Flat 4 6
Mic Jack Insulating Washers, Shoulder 4 6
Intercom Panel - lettered on both sides. 1 1
Intercom Control Knobs 4 4
Mounting Screws 4-40 x 1/2 2 2
Drill Template - Adhesive backed hole size
pattern for drilling aircraft panel 1 1
Aircraft /IntercomInterface Cable
(4 feet long) 1 1
Headphone/Music Interface Cable
(4 feet long) 1 1
Stereo music input jacks 3.5mm 2 2
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.

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SHOULDER
WASHER
FLAT
INSULATED
WASHER
FLAT
METAL
WASHER
NUT
AIRCRAFT
PANEL
RING
BARREL
TIP
Figure 3
Microphone Jack
KNOB
KNOB
Figure 2
AIRCRAFT PANEL INTERCOM PANEL
DO NOT REMOVE
THESE NUTS
SCI INTERCOM CHASSIS
4-40 SCREWS
UP
RX. ADJ. MOD. ADJ.
Figure 2Figure 1
INTERCOM OPTIONS
The SCI-S intercoms have two options that can be enabled if desired.
Installing small jumper wires on the solder side of the circuit board
enables these options. As such they have to be installed before the unit
is installed into the aircraft.
OPTION “A” - FULL 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. If you prefer
however, the music can be completely muted during intercom if you
enable this option. Note - during radio transmission and reception, the
music will always be fully muted regardless if this option is selected or
not. This is for communication safety reasons.
OPTION “B” - PILOT TRANSMIT PRIORITY - If the pilot and the copilot
key at the same time (not a common occurrence) the default operation is
that both microphones will go out the aircraft radio to the tower. If you
prefer only the pilot’s microphone active when both press their PTT’s
simultaneously then enable this option. Note - if only one of the pilots
presses his PTT only his mic will go out over the radio regardless if this
option is selected or not.
To enable either or both of these options, remove the four screws on
the bottom of the SCI-S unit and remove the cover. Refer to Figure 1.
To enable option A (full music mute during ICS), solder a small jumper
from the pad labeled “A” to the pad labeled “G”. To enable option B (pilot
transmit priority) solder a small jumper between pad “B” and pad “G”.
Replace the cover and the four screws and tighten. Removing these
jumpers will deactivate the options.
CHASSIS INSTALLATION
To upgrade an existing SPA-400 installation to an SCI-S4 or a SPA-600 to an
SCI-S6 skip to the “UPGRADING A SPA INSTALLATION TO A SCI-S” section
on page 4. For a completely new intercom installation, continue below.
UNIT PLACEMENT
The SCI-S unit has been designed to mount either horizontally or vertically
in your aircraft panel. The location selected for the SCI-S unit requires
a minimum front panel area of 2½” by 1”. Depth required behind panel
is 6” 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 in-
tercom and cable will not interfere with any aircraft control components.
Panel Preparation
1. Position the adhesive drill template on the aircraft panel in the se-
lected area.
2. Center punch each hole at the cross lines. (Five holes are in a straight
line and equally spaced 0.4” apart. The two Squelch Indicator Light
holes are 0.8” apart).
3. Drill ⁄” pilot holes in all seven places.
4. Enlarge two holes to ⁄”, one hole to ⁄”, and two holes to ⁄” per
the template.
MOUNTING CHASSIS (See Figure 2)
1. Remove the knobs from the Volume and Squelch controls using
a 0.050” Allen wrench. NOTE: DO NOT REMOVE the nuts from the
Volume/Squelch, or ALL / ISO / CREW controls.
2. Insert the SCI-S unit from the rear of the aircraft panel with the appropri-
ate arrow on the unit chassis pointing upwards. Make sure the squelch
indicator lights have unrestricted movement through aircraft panel.
3. Install the printed SCI-S panel and lightly thread the two 4-40 screws
through the holes in intercom panel. The nuts on the Volume/Squelch
and ALL / ISO / CREW controls will t inside the ⁄” and ⁄” diameter holes.
4. Tighten the two screws.
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

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12345
AIRCRAFT RADIO
INTERCOM
CIRCUIT
BREAKER
(1 AMP)
ALL
ISO
CREW
SCI-S
Pilot/CoPilot
Made in U.S.A.
S
Q
Volume
Passenger
A
TO
A
TO
++
PASSENGER MUSIC
INPUT JACK +
MUSIC SOURCE ++
++
PASSENGER MUSIC
INPUT JACK +
MUSIC SOURCE ++
HEADPHONE
JACK
BARREL
TIP
BARREL
TIPRING
MICROPHONE
JACK
PASSENGER 4*
TO
RING A
HEADPHONE
JACK
BARREL
TIP
BARREL
TIPRING
MICROPHONE
JACK
PASSENGER 3*
TO
RING A
HEADPHONE
JACK
BARREL
TIP
BARREL
TIPRING
MICROPHONE
JACK
PASSENGER 2
TO
RING A
HEADPHONE
JACK
BARREL
TIP
BARREL
TIPRING
MICROPHONE
JACK
PASSENGER 1
TO
RING A
HEADPHONE
JACK
BARREL
TIP
BARREL
TIPRING
MICROPHONE
JACK
PILOT
TO
RING A
HEADPHONE
JACK
BARREL
TIP
BARREL
TIPRING
MICROPHONE
JACK
CO-PILOT
TO
RING A
NOTES:
* USED IN SCI-S6 INSTALLATIONS ONLY.
** IF PILOT PTT SW IS CONNECTED TO THE
AIRCRAFT HAND MIC JACK, IT MUST BE
DISCONNECTED AND CONNECTED TO
THE WHITE/RED WIRE AS SHOWN.
+ FOR SINGLE MUSIC SOURCE OR CAR
STEREO WIRING SEE PART 6 UNDER
"WIRING INSTRUCTIONS" IN THE SCI-S4 /
SCI-S6 INSTALLATION INSTRUCTIONS.
++ MUSIC SOURCE AND CONNECTING
CORD ARE CUSTOMER SUPPLIED.
AIRCRAFT CHASSIS GROUND.
AIRCRAFT/INTERCOM INTERFACE AREA
SCI-S
INTERCOM
TO AIRCRAFT
POWER BUSS
12/28 VDC INTERCOM
CENTRAL
GROUND
POINT
POINT A
MIC AUDIO
HEADPHONE AUDIO
AIRCRAFT
HAND MIC
JACK
AIRCRAFT
HEADPHONE
JACK
RADIO MIC KEY
TIP TIP
RING
J1 (3) BLUE
J1 (6) BROWN
J1 (7) RED J1 (4) BLACK
P1
J1
J1 (14) TAN*
J1 (13) TAN*
J1 (5) WHITE
P2
J2
J1 (2) WHITE/RED **
J1 (10) WHITE/BLUE
P2 (3) YELLOW
J1 (8) TAN J1 (9) TAN
P2 (9) WHITE/YELLOW
P2 (3) YELLOW
P2 (9) WHITE/YELLOW
P2 (7) WHITE/GREEN
P2 (8) WHITE/GRAY
P2 (4) ORANGE
P2 (5) BLACK
P2 (6) VIOLET
BARREL
TIP
RING
P2 (10) WHITE/BROWN
P2 (11) BLACK
P2 (12) WHITE/VIOLET
BARREL
TIP
RING
P2 (1) GREEN
P2 (1) GREEN
P2 (2) GRAY
P2 (2) GRAY
J1 (1) WHITE/BLACK
J1 (11) WHITE/ORANGE
PILOT
PTT SWITCH
CO-PILOT
PTT SWITCH
SCI-S4 / SCI-S6 INSTALLATION WIRING DIAGRAM
Figure 4
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 N/C None No Connection
13 Tan *5 Passenger #3 Mic Input Ring Terminal of Passenger #3
Intercom Mic Jack
14 Tan *5 Passenger #4 Mic Input Ring Terminal of Passenger #4
Intercom Mic Jack
15 N/C None No Connection
TABLE 2 - J2 / P2 - See Wiring Instructions
PIN WIRE COLOR FUNCTION CONNECT TO
1 Green *7 Pilot Intercom Right
Headphone Output
Tip Terminal of Pilot
Headphone Jack
2 Grey *7 Co-Pilot Intercom Right
Headphone Output
Tip Terminal of Co-Pilot
Headphone Jack
3 Yellow *7
Passenger Intercom
Right Headphone
Output
Tip Terminal of Passenger
Headphone Jacks
4 Orange *6 Crew Music Input
Left Channel
Left Crew Music Source
Headphone / Line output
5 Black *6 Crew Music Input
Common
Crew Music Source
Common Headphone / Line Output
6 Violet *6 Crew Music Input
Right Channel
Right Crew Music Source
Headphone / Line output
7 White / Green *7 Pilot Intercom Left
Headphone Output
Ring Terminal of Pilot
Headphone Jack
8 White / Grey *7 Co-Pilot Intercom Left
Headphone Output
Ring Terminal of Co-Pilot
Headphone Jack
9 White / Yellow *7
Passenger Intercom
Left Headphone
Output
Ring Terminal of Passenger
Headphone Jacks
10 White / Brown *6 Passenger Music Input
Left Channel
Left Passenger Music Source
Headphone / Line output
11 Black *6 Passenger Music Input
Common
Passenger Music Source
Headphone / Line Common Output
12 White / Violet *6 Passenger Music Input
Right Channel
Right Passenger Music Source
Headphone / Line outputt

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-
RIGHT
LEFT
STEREO
+
+
-
+-
+-
RC
R
R - 100 OHM, 5 WATT RESISTOR
C - 220 MFD, 25 VOLT CAPACITOR
NO CONNECTION
NO CONNECTION
TO INTERCOM
P2 (6) VIOLET
P2 (4) ORANGE
P2 (5) BLACK
P2 (12) WHITE/VIOLET
P2 (10) WHITE/BROWN
P2 (11) BLACK
Figure 6
C
Figure 5
TIP
(RIGHT)
RING
(LEFT)
BARREL
(COMMON)
AIRCRAFT PANEL
NUT
with any aircraft control components. (Note that the jack contacts will
expand when a plug is inserted into the jack.)
2. Drill ⁄” 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 wire to the barrel terminal of the mic jack and
connect the other end to 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 con-
nection. Connect the white/green wire (P2 pin 7) to the ring connection.
WIRING INSTRUCTIONS
Connections should be made as shown in Figure 4 and indicated in
Tables 1 and 2. If longer wire lengths are required, use a good quality
hook-up wire - 22 gauge or larger. Although not necessary, shielded
audio wire can be used if desired. This can simplify the wiring process.
1. The blue wire from Pin 3 must be connected to the aircraft radio
headphone output - NOT the speaker output.
2. Connect all intercom mic jack grounds to a single aircraft chassis ground
point - Point “A” - as shown in Figure 4. (Use the black washers sup-
plied 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 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 Point “A”. It is not necessary, however, to connect the headphone
jack barrels to Point “A”. They can either be grounded where they are
mounted or some place nearby.
3. The red wire may be con-
nected 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, 13,
14) are only used on instal-
lations that require extra
intercom positions.
5. Tan wires pins 13 and 14 are
provided on SCI-S6 units only.
6. The SCI-S system provides two separate music inputs - one for the
crew and the other for the passengers. These music inputs accept
Headphone (Walkman) or Line level music sources. The wiring diagram
shows how to wire the SCI-S for dual music inputs for use with por-
table stereo music sources. Two small stereo input jacks are supplied
for this purpose. Connect the Orange, Violet, and Black wires to one
jack as shown in Figure 4. Identify the jack terminals using Figure 5.
Connect the White/Brown, White/Violet, and Black wires to the second
jack. Drill a ¼” hole for each 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.
If only a single portable music source is to be used there are two dierent
methods this can be done. The rst way and most exible is to wire just
like the wiring drawing and use a mini-jack “Y” or splitter (also available
at your local Stereo or electronics store) and dual cables to go from one
stereo into both crew and passenger input jacks. The second way is to
use just one of the supplied music input jacks and connect both inputs
to it. Do this by connecting both the Orange and the White/Brown wire
to the TIP terminal, the Violet and White/Violet to the RING, and both
Blacks to the BARREL.
Speaker level output car stereo music sources can also be used with the
SCI-S system. A Floating Ground Adapter or a four wire to three wire
converter will have to be used between the Stereo and the SCI-S music
inputs. Figure 6 shows such an adapter and how it is wired into the SCI-S.
7. The Sigtronics SCI-S 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 SCI-S 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 pilot jack, WHITE/GREY and GREY on
the copilot’s and WHITE/YELLOW and YELLOW on the passengers.
8. Make sure any unused wires are properly insulated and kept from
shorting to any other wires or aircraft ground. Skip down to the
“INSTALLATION CHECK OUT AND ADJUSTMENT” section on page 5.
UPGRADING A SPA INSTALLATION TO A SCI-S
Chassis Mounting
The SCI-S4 is specically designed to easily replace a SPA-400. Similarly,
the SCI-S6 can replace a SPA-600. The panels are exactly the same di-
mensions (1” x 2½”), however the SCI-S units are 1⁄” longer than the SPA
units. You will have to make sure that you have the extra depth required
behind your panel. Five mounting holes are exactly in the same posi-
tions. The center hole will have to be enlarged from ¼” to ⁄”, the two
outer holes will have to be enlarged to ⁄”, and two additional holes
drilled to ⁄” (As per template).

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To upgrade, rst remove the SPA unit 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 panel. Pull the SPA unit out
and unplug the white connector from the wiring harness. Next, drill the
center hole in the aircraft panel out to ⁄”. Then drill the two outer holes
to ⁄”, then use template to mark the position of the nal two holes and
drill. Finally mount the SCI-S chassis (see Figure 2):
1. Remove the knobs from the Volume and Squelch controls using a 0.050”
Allen wrench. NOTE: DO NOT REMOVE the nuts from the Volume/
Squelch (VOL/ SQ) or ALL / ISO / CREW controls.
2. Insert the SCI-S unit from the rear of the aircraft panel with the ap-
propriate arrow on the unit chassis pointing upwards. The squelch
indicator lights (LED’s) should easily t through their respective holes.
3. Install the printed SCI-S panel and lightly thread the two 4-40 screws
through the holes in intercom panel. The nuts on the Volume/Squelch
and ALL / ISO / CREW controls should t inside the aircraft panel holes.
4. Tighten the two screws. Make sure LED’s have unrestricted movement
in aircraft panel holes.
5. Put the knobs on the Volume and Squelch control shafts and tighten
the Allen screws.
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 or 15 pin) that comes with
the SCI-S system. You will use the SPA harness already in the aircraft and
the 4-foot Headphone/Music interface cable (12 pin).
In a SPA installation, the tip terminals of the pilot, co-pilot, and pas -
senger 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.
INSTALLATION CHECK-OUT AND ADJUSTMENTS
After the unit is installed, again check that the SCI-S unit chassis, jacks,
and wiring harness are clear of all aircraft operating controls and cause
no interference with them. Next, to check out the SCI-S 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, as is the practice with a hand-held mic. 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, remove power to the SCI-S by
pulling intercom circuit breaker. 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 us-
ing his push-to-transmit switch and headset. Aircraft radio(s) and audio
panel should operate exactly as they did before the SCI-S system was
installed. Aircraft radio reception should not be heard in the co-pilot or
passenger headsets. There should be no intercom between headsets
without power applied to the SCI-S unit.
Next restore power to the SCI-S unit. Switch ALL / ISO / CREW control
to the “ALL” position. Set the SCI-S volume controls to mid-position.
Set both SCI-S squelch controls fully clockwise. Pilot can operate the
aircraft radio(s). In this mode all headsets on the intercom will hear the
aircraft radio(s).
SCI-S4 / SCI-S6 AUDIO PRIORITY TABLE
AUDIO MODE – ALL
AUDIO IS MUTED BY:
MODE – ISO
AUDIO IS MUTED BY:
MODE – CREW
AUDIO IS MUTED BY:
PILOT MIC Co-pilot PTT* Never Muted Co-pilot PTT*
CO-PILOT MIC Pilot PTT* Co-pilot PTT Pilot PTT*
PASSENGER MICS Pilot PTT or Co-pilot PTT Never Muted Never Muted
PILOT ATC RADIO Pilot PTT or Co-pilot PTT Never Muted Pilot PTT or Co-pilot PTT
CO-PILOT ATC RADIO Pilot PTT or Co-pilot PTT Always Muted Pilot PTT or Co-pilot PTT
PASSENGER ATC RADIO Pilot PTT or Co-pilot PTT Always Muted Always Muted
CREW MUSIC ** Pilot PTT, Co-pilot PTT, ATC, Crew ICS, or Pass ICS Co-pilot PTT, Co-pilot ICS, or Pass ICS Pilot PTT, Co-pilot PTT, ATC, or Crew ICS
PASS MUSIC ** Pilot PTT, Co-pilot PTT, ATC, Crew ICS, or Pass ICS Co-pilot PTT, Co-pilot ICS, or Pass ICS Passenger ICS
NOTES: ATC - Aircraft VHF Radio. Crew - Pilot and Co-pilot. ICS - Intercom Audio. PTT - Push-To-Transmit Switch.
* Pilot Mic will always go out over the VHF radio when his PTT is keyed. Co-pilot Mic will also go out when both PTT’s are pressed,
unless the “Pilot Transmit Priority” option is enabled.
** Music sources will partial mute on ICS, unless the “Full Music Mute During ICS” option is enabled.
SCI-S4 / SCI-S6 MODE SELECTION TABLE
MODE PILOT HEARS CO-PILOT HEARS PASSENGERS HEAR
ALL ATC, Crew ICS, Pass ICS, Crew Music ATC, Crew ICS, Pass ICS, Crew Music ATC, Crew ICS, Pass ICS, Pass Music
ISO ATC Co-pilot ICS, Pass ICS, Crew Music Co-pilot ICS, Pass ICS, Pass Music
CREW ATC, Crew ICS, Crew Music ATC, Crew ICS, Crew Music Pass ICS, Pass Music

Page 6 SigtronicS Sci-S Panel Mount intercoMS www.SigtronicS.coM
It may be necessary at this time to adjust the SCI-S 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 SCI-S 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).
It may also be necessary to adjust the SCI-S unit radio receive input from
the aircraft radio. A small adjustable potentiometer is provided inside
the unit for this purpose. It is accessible through a hole in the side of
the SCI-S chassis. It is marked “RX Adj.”, and can be adjusted with a small
blade screwdriver (See Figure 2). In the event of low aircraft radio volume
in the “ALL” or “CREW” mode relative to “ISO” mode, an appropriate
adjustment can be made. Clockwise rotation increases the input level
to the SCI-S 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 the pilot and co-pilot headsets plugged in. (The input is set
full CCW which is unity gain for 500Ω radios).
You are now ready to check for proper wiring of the music sources. First,
make sure both squelch lights are o and intercom is in ALL mode. Turn
on the crew music source and listen for music through pilot and co-pilot
headsets. There should be music. Then switch to CREW mode. There
should also be music in both pilots’ headsets. Similarly, turn on the pas-
senger music source. There should be music in the passenger headsets.
If everything checks out, refer to the MODE SELECTION and AUDIO
PRIORITY TABLES as well as the separate SCI-S4/SCI-S6 OPERATING
INSTRUCTIONS sheet for proper use and other operating modes of
the Sigtronics SCI-S 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 SCI-S intercom or any other Sigtronics
product feel free to contact us directly or email us at tech@sigtronics.
com. Technicians are available Monday though Friday 8 am to 4:30 PM
Pacic time.
This concludes the installation check-out.
Stereo Music Systems
Most automotive stereo units operate from 12V-14V sources. If you
want to use these in a 28 volt aircraft do not connect them directly to
power. Regulators or converters are available to permit operation from
24V-28V sources.
Some AM-FM music receivers are capable of causing interference with
aircraft COM and NAV receivers. The aircraft panel should be placarded
accordingly. Most player only units (cassette or CD) do not cause interfer-
ence with aircraft receivers.
Line level stereo music outputs can also be used into the SCI-S system.
Some line level outputs however, are a xed level and are not adjusted
by the devices volume control. If this is the case you will not be able to
change the volume of the music you hear in the headsets. Headphone
level or Speaker level outputs would be better in this case.
Stereo Headsets
The Sigtronics SCI-S systems are designed for use with general avia-
tion Stereo headsets with high impedance speakers (300 to 600 ohms).
Headsets with low impedance (less than 100 ohms) speakers should not
be used with SCI-S systems without modication. Contact Sigtronics
for details. In general, headsets with speakers of high and low imped-
ance and/or unmatched audio eciencies should not be used together
without modications.
Sigtronics stereo headsets are specically designed for the aircraft high
noise environment and give excellent noise attenuation. They also
provide full frequency response stereo for maximum enjoyment. They
are compatible with aircraft mic circuits and can be used as general avia-
tion headsets in aircraft that are not equipped with stereo headphone
jacks. This is because they include a switch to change from “Stereo” to
“Monaural”. No adapters required.
NOTE: General aviation headset (monaural) phone plugs should not be
plugged into SCI-S stereo phone jacks. A monaural plug in a stereo jack
shorts out one of the audio channels. This will not damage the SCI-S
system in any way but will cause reduced performance. General aviation
headsets may be used only if one of the following three changes are made:
1. Monaural to stereo adapters are used on the headset head-phone
plugs. (Only monaural music will be heard.)
2. The general aviation headsets are re-wired for stereo reception.
3. Install the Sigtronics SCI-S system for monaural operation. See note
6 on page 4 in the “WIRING INSTRUCTIONS” section.
See the separate SCI-S4/SCI-S6 OPERATING INSTRUCTIONS sheet for
complete operation information.
SCI-S_REV-D_Installation.pdf 8-8-2023 P/N 700112
Sigtronics Corporation
178 East Arrow Highway
San Dimas, Ca 91773
909) 305-9399
www.sigtronics.com