Sigtronics SPA-4Si - Manual (Page 2)

INTERCOM
PANEL
4–40 SCRE WS
SWITCH
NUT
INTERCOM
DO NOT REMOVE
THESE NUTS
KNOB
KNOB
AIRCRAFT
PANEL
Figure 2
SHOULDER
WASHER
FLAT
INSULATED
WASHER
FLAT
METAL
WASHER
NUT
AIRCRAFT
PANEL RING
BARREL
TIP
Microphone Jack Figure 3
page 2
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.
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. See page 5.
HIGH NOISE VERSION
Model SPA-4SiH – The “H” version of the SPA-4Si has all the above features
but is specifically configured for very high noise environments.
CHASSIS INSTALLATION
UNIT PLACEMENT
For ease of operation we recommend that you place the pilot’s SPA-4Si
unit on the pilot’s side of the aircraft panel and the co-pilot’s unit should
be placed on his side. This eliminates any confusion about which half of
the system each pilot has to operate. Also, the location selected for each
SPA-4Si unit requires a minimum front panel area of 2-1/2” by 1”. Depth
required behind panel is 4” plus cable access.
CAUTION: Move the aircraft flight controls through the limits of travel while
observing the selected area and making sure that the rear of the intercoms
and cables will not interfere with any aircraft control components.
PANEL PREPARATION EACH UNIT:
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 five places.
4. Enlarge holes to 1/4” and 3/8” per the template.
MOUNTING CHASSIS (See Figure 2)
1. Remove the knobs from the Volume and Squelch controls using a 0.05
inch 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-4Si unit from the rear of the aircraft panel with the
appropriate arrow on the unit chassis pointing upwards.
3. Install the printed SPA-4Si panel and lightly thread the two 4-40 screws
through the holes in intercom panel. The nuts on the Volume and Squelch
controls will fit 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 1/2” 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 (J1 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 adjustment to the radio receive potentiometer will fix this. See
“INSTALLATION CHECK-OUT AND ADJUSTMENTS” Radio Receive Adjust
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, all intercom
ground wires (J1 pin 4) and all PTT switch ground returns 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) and White/Orange (J1 Pin 11) are only used on
installations that require passenger intercom positions.