Sigtronics SPA-400 User manual

Figure 1
Figure 2
4–40 SCREWS SWITCH
NUT
KNOB
KNOB
AIRCRAFT PANEL
INTERCOM PANEL
DO NOT
REMOVE
THESE
NUTS
INTERCOM CHASSIS
MOD. ADJ.
INTRODUCTION
ATTENTION INSTALLER: To assure a trouble free installation, please
read the entire instructions through once before beginning.
The Sigtronics’ SPA-400 is a voice actuated (VOX) intercom for up to four
headset positions with transmit through the aircraft radio capability
using your push-to-talk switches.
Three controls are provided:
Power Switch — Turns unit on and o.
Volume Control — Controls the intercom volume.
Squelch Control — Allows the setting of voice actuated (VOX)
operation of the intercom for variations in background noise levels
and dierences in headset microphones.
SPA-400 SYSTEM SPECIFICATIONS
CONFIGURATION – The SPA-400 Intercom system is specically
designed for permanent, panel mounted installation in aircraft.
COMPATIBILITY – Sigtronics SPA-400 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: 4.5 ounces (SPA-400 intercom unit with panel and knobs).
Jacks and wiring harness weigh (5.5 ounces maximum).
INPUT POWER: 11 VDC through 32 VDC. Maximum current drain 0.06
amps @ 28 volts
WARRANTY: SPA-400 intercoms are constructed of high quality
components and carry a ve year parts and labor warranty.
FAA TSO: C50b ENV. CAT (DO-160) CFBBBX
HARDWARE SUPPLIED
Intercom unit, instructions, and the following hardware:
Headphone Output Jacks - Accept standard 0.250” aircraft
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. ..................................................................... 4
Mic Jack Insulating Washers, Flat ........................................................... 4
Mic Jack Insulating Washers, Shoulder ................................................ 4
Intercom Panel - lettered on both sides. ............................................. 1
Intercom Control Knobs ............................................................................ 2
Switch Nut ....................................................................................................... 1
Mounting Screws 4-40 x ½ ....................................................................... 2
Drill Template - Adhesive backed hole size pattern for
drilling aircraft panel. ................................................................................. 1
Aircraft / Intercom Interface Cable (4 feet long) ............................... 1
CHASSIS INSTALLATION
The Sigtronics’ SPA-400 has been designed to mount either horizontally
or vertically in your aircraft panel. All necessary mounting hardware
has been supplied for a 4-way installation. (A round faceplate is also
available from Sigtronics to t a 2¼” round instrument hole).
The location selected requires a minimum front panel area of 2½” by
1”. Depth required behind panel is 4
³⁄” plus cable access.
Caution: Move aircraft ight controls through limits of travel while
observing selected area to make sure rear of intercom and cable will
not interfere with aircraft control components.
PANEL PREPARATION:
1. Position adhesive template on aircraft panel in selected area.
2. Center punch each hole at cross lines. (The ve holes are in straight
line and equally spaced 0.4” apart.)
3. Drill ¹⁄” pilot hole all ve places.
4. Enlarge holes to ¼” and ³⁄” per template.
MOUNTING CHASSIS: See Figure 2.
1. Remove switch nut from intercom ON-OFF switch bushing.
2. Remove knobs from Volume and Squelch controls. NOTE: DO NOT
REMOVE nuts from Volume and Squelch control potentiometers.
3. Remove two 4-40 panel screws and remove panel from the chassis.
Sigtronics SPA-400 TSO Installation and Operating Instructions
Specialists in “SOUND” Management
178 East Arrow Highway, San Dimas, CA 91773 ( 909 ) 305-9399
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.

Sigtronics Corporation
178 East Arrow Highway
San Dimas, CA 91773
909) 305-9399
www.sigtronics.com
SHOULDER
WASHER
FLAT
INSULATED
WASHER
FLAT
METAL
WASHER
NUT
AIRCRAFT
PANEL
RING
BARREL
TIP
Figure 3
Microphone Jack
4. Insert the intercom from rear of aircraft panel with appropriate UP
arrow for horizontal or vertical installation.
5. Install panel and lightly thread nut on to ON-OFF switch. Nuts and
washers on Volume and Squelch controls should t inside the ⁄”
diameter holes.
6. Install the two 4-40 screws through the intercom and aircraft panel
holes into the intercom. Tighten ON-OFF switch nut.
7. Install knobs on Volume (VOL) and Squelch (SQ) control shafts using
.050” Allen wrench.
MOUNTING HEADPHONE AND MICROPHONE JACKS:
1. Select mounting areas. (One mic and one headphone jack for each
headset). Again, make sure the jacks will not interfere with aircraft
control components.
2. Drill
⁄” diameter holes for headphone jacks and install.
3. Drill ½” diameter holes for mic jacks and install with insulating
washers supplied. (See Figure 3).
WIRING INSTRUCTIONS
Connections should be made as shown in Figure 4 and indicated in Table 1
*A. White / red (pilot push-to-talk) must correspond with white / black
(pilot mic input) as shown.
*B. The blue wire from Pin 3 must be connected to the aircraft radio
headphone output- NOT the speaker output.
*C. Connect all intercom mic jack grounds to Point A as shown in Figure
4. (Use black washers supplied to insulate intercom mic jacks from
aircraft chassis ground).
*D. Do NOT connect transmit switches to white (key) wire.
*E. Red wire may be connected to either 12 (14V) or 24 (28V) power
source. No switching or adjustments are required to operate from
either source.
*F. Tan wires from Pins 8 and 9 are only used on 4-way installations.
FINAL CHECKOUT AND ADJUSTMENT
After the unit is installed, again check that the intercom chassis, jacks,
and wiring harness are clear of all aircraft operating controls and cause
no interference with them. Check out the intercom functions by following
the Operating Instructions.
It may be necessary at this time to adjust the intercom mic output to
the aircraft radios. A small, square, adjustable trimmer potentiometer is
provided inside the unit for this purpose. It is accessible through a hole
in the side of the case, marked “Mod. Adj.”, and can be adjusted with
a 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
initial installation of the intercom or if a new radio is installed. (The
output is set for unity gain at Sigtronics.)
OPERATING INSTRUCTIONS
I. INTERCOM MODE
A. Put on headset/s and position the boom mic close to the mouth,
as is the practice with a hand-held mic. Voice clarity is best when
mic is at one side of the mouth and ¼” from the lips.
B. Set audio panel to “Headphone” position, if applicable.
C. Turn power “on” and set Volume Control to a low level. (1/4th to
1/3rd open for best signal to noise ratio).
D. To adjust the intercom SQuelch for voice activated operation
(VOX), it is helpful to have some background noise present. Turn
intercom SQuelch control all the way counter-clockwise. Now,
without speaking, rotate the SQuelch control clockwise until you
hear the background noise in your headset. Next, rotate it counter-
clockwise a small amount and wait (approximately 1 second) until
the background noise disappears. Finally, make small adjustments
until your voice triggers the unit at comfortable speaking levels.
This procedure is necessary because the squelch is a “Fast-on,
Slow-o” system.
Once set, the intercom stays silent until someone speaks in their
headset microphone (mic). Then it instantly turns on and relays
the conversation. After about a second of no conversation, the
intercom goes silent again.
Minor readjustment of the SQuelch may be necessary if the
background noise level changes signicantly (such as from taxi
to take-o power conditions).
II.RADIO TRANSMIT MODE — Transmitting from both pilot and co-
pilot positions is possible on a one-at-a-time basis. The transmitting
mic disables all other mics. When you are ready to talk to ATC, depress
the transmit switch on your yoke and your voice is automatically
transmitted via the aircraft radio. (You will hear your own voice
when transmitting via the aircraft radio side-tone return, If the radio
does not have side-tone, then you will not hear your voice). (A minor
modication to the intercom will enable it to simulate side-tone).
III. RADIO MONITORING — Radio monitoring is automatic. The radio
monitor circuit is always active; even with intercom power switch
“o”.
IV. SOLO FLIGHTS — Since the intercom is not needed during solo
ights, it may be turned o. The pilot will still hear the aircraft radio,
since this circuit is always active, and the pilot may transmit to ATC
via his push-to-talk switch. (Co-pilot position cannot transmit when
intercom is o).
V. BACK-UP — If a problem is suspected in the intercom, simply turn it
o. You will still receive the aircraft radio and will be able to transmit
from the pilot’s position. The hand mic may also be used, however,
the intercom should be turned o and the pilot’s mic plug unpluged
from the mic jack. (Leave the headset headphone plug plugged in
for radio reception).

12345
AIRCRAFT RADIO
MIC AUDIO
HEADPHONE AUDIO
RADIO MIC KEY
INTERCOM
CIRCUIT
BREAKER
(1 AMP)
TO TO
INTERCOM SPA-400
SPA-400
INTERCOM
SQ ON VOL
TO AIRCRAFT
POWER BUSS
12 / 28 VDC
POINT A
(INTERCOM
CENTRAL
GROUND
POINT) AIRCRAFT
HEADPHONE
JACK
AIRCRAFT / INTERCOM
INTERFACE AREA
PILOT
PTT SWITCH CO-PILOT PTT SWITCH
(3) BLUE
(4) BLACK (7) RED
(3) BLUE
(8) TAN
(11) WHITE / ORANGE
(10) WHITE / BLUE
(2) WHITE / RED
(5) WHITE
(6) BROWN
(1) WHITE / BLACK
TIP
TO
HEADPHONE
JACK
BARREL
TIP RING
MIC
JACK
BARREL
TIP
CO-PILOT
TO
HEADPHONE
JACK
BARREL
TIP RING
MIC
JACK
BARREL
TIP
PILOT
TO
HEADPHONE
JACK MIC JACK
PASSENGER 2
BARREL
TIP RING
BARREL
TIP
TO
HEADPHONE
JACK MIC JACK
PASSENGER 1
BARREL
TIP RING
BARREL
TIP
P1
J1
RING
AIRCRAFT
HAND MIC
JACK
TIP
(9) TAN
SPA-400 Installation Drawing Figure 4
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.
2. AIRCRAFT CHASSIS GROUND.
Table 1
Plug Pin # Wire Color Function Connect To:
1White / Black Pilot Mic Input Ring Terminal of Pilot Intercom Mic Input Jack
2White / Red *A Pilot Transmit Switch Input Pilot Transmit Switch (PTT) (Switch to Ground to Transmit)
3Blue *B Headphone - Radio and Intercom Outputs Radio Headphone Output and all Headphone Jacks
4Black *C Ground Hand Mic Jack Ground Terminal (Point A)
5White *D Transmit Relay (Key) Control Output Tip Terminal of Aircraft Mic Jack or Key Input of Aircraft Radio or Audio Panel
6Brown Mic Audio Output Ring Terminal of Aircraft Mic Jack or Input of Aircraft Radio or Audio Panel
7Red *E 12 VDC through 24 VDC Power Input Intercom Circuit Breaker
8Tan *F Passenger #1 Mic Input Ring Terminal of Passenger #1 Mic Jack
9Tan *F Passenger #2 Mic Input Ring Terminal of Passenger #2 Mic Jack
10 White / Blue Copilot Transmit Switch Copilot Transmit Switch (PTT)
11 White / Orange Copilot Mic Input Ring Terminal of Intercom Copilot Mic Input Jack
12 —No Connection
* See Wiring Instructions
SPA-400_REV-I_Installation_Operating.pdf 8-8-2023 P/N 700013