Sigtronics SPA-400 User manual

SPA-400 TSO INSTALLATION AND OPERATING INSTRUCTIONS
TheSigtronics’SPA-400isavoiceactuatedintercomwith“transmitthrough
the aircraft radio capability” using your push-to-talk switch. Three controls
are provided:
Power Switch — Turns unit on and off.
Volume Control — Controls the intercom volume.
SquelchControl —Allowsthesettingofvoiceactuated (VOX) operation of
the intercom for variations in background noise levels and differences in
headset microphones.
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 1/4" 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-off”
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 significantly (such as from taxi to
take-off 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
modification 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
“off”.
IV. SOLOFLIGHTS—Sincetheintercomisnotneeded duringsoloflights,
it may be turned off. 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 the inter-
com is off).
V. BACK-UP — If a problem is suspected in the intercom, simply turn it off.
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 off and you should unplug your boom mic
from the mic jack. (Leave headphone plugged in for radio reception).
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 fit a 2 1/4" round instrument hole.)
HARDWARE SUPPLIED
Four Headphone Output Jacks- Accept standard .250" aircraft headphone
plugs.
Four Microphone Input Jacks- Accept standard .206" aircraft microphone
plugs (i.e. carbon or amplified dynamic). (U93 plug compatible jacks can be
used in place of the jacks provided).
Mic Jack Insulating Washers: 4 shoulder and 4 flat.
Intercom Panel: Lettered on both sides.
Control Knobs (2), Switch Nut (1), 4-40 Screws (2)
Template: Hole size pattern for drilling aircraft panel.
Aircraft/Intercom interface cable (4 feet long)
The location selected requires a minimum front panel area of 2 1/2" by
1 1/16". Depth required behind panel is 4 3/16" plus cable access.
Caution: Move aircraft flight 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. Centerpuncheachholeat crosslines.(Thefiveholesarein straightline
and equally spaced 0.4" apart).
3. Drill 1/8" pilot hole all five places.
4. Enlarge holes to 1/4" and 3/8" per template. MOUNTING CHASSIS: See Figure 2.
1. Remove nut from the 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 intercom
chassis.
4. Insert intercom from rear of aircraft panel with appropriate arrow
pointing upwards.
(continued)
FIGURE 2
PHONE [phone]
949 N. Cataract Ave. #D, San Dimas, CA 91773
FIGURE 1

MOUNTING CHASSIS (continued)
6. Select two 4-40 screws through holes in intercom panel. 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 3/8" diameter holes for headphone jacks and install.
3. Drill1/2"diameterholesformicjacks andinstallwithinsulatingwashers
supplied. (See Figure 3).
WIRING INSTRUCTIONS
ConnectionsshouldbemadeasshowninFigure4andindicatedinTableI
*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. ConnectintercommicjackgroundstoPointAasshowninFigure4.
(Useblack washers supplied toinsulateintercommicjacksfromaircraft
chassis ground).
*D. Do NOT connect transmit switches to white (key) wire.
*E. Redwiremaybeconnectedtoeither12(14V)or24(28V)powersource.
Noswitchingoradjustmentsarerequiredtooperatefromeithersource.
*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
providedinsidetheunitfor thispurpose.Itisaccessiblethrougha holeinthe
side of the case, marked “Mod. Adj.”, and can be adjusted with a
screwdriver. In the event of overmodulation (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).
Weight: Intercom with panel and knobs (4.5 oz.)
Jacks and wiring harness (5.5 oz. maximum)
The SPA-400 is FAA-TSO approved (C-50b).
Env. Cat (D0-160) CFBBBX
PLUG
PIN#
1
2
3
4
5
6
7
8
9
10
11
12
WIRE COLOR
White/Black
White/Red *A
Blue *B
Black *C
White *D
Brown
Red *E
Tan *F
Tan *F
White/Blue
White/Orange
FUNCTION
Pilot Mic Input
Pilot Transmit
Switch Input
Headphone - Radio
and intercom Outputs
Ground
Transmit Relay (Key)
Control Output
Mic Audio Output
12 Through 24 VDC
Power Input
Passenger #1
Mic Input
Passenger #2
Mic Input
Co-Pilot Transmit
Switch
Co-Pilot Mic Input
CONNECT TO:
Ring Terminal of Pilot
Intercom Mic Input Jack
Pilot Transmit Switch (PTT)
(Switch to Ground to Transmit)
Radio Headphone Output and
all Headphone Jacks
Hand Mic Jack Ground
Terminal (Point A)
TipTerminalofAircraftMicJack
or Key Input of Aircraft Radio or
Audio Panel
Ring Terminal of Aircraft Mic
Jack or Input of Aircraft Radio
or Audio Panel
Intercom Circuit Breaker
Ring Terminal of Passenger #1
Mic Jack
Ring Terminal of Passenger #2
Mic Jack
Co-Pilot Transmit Switch (PTT)
Ring Terminal of Intercom
Co-Pilot Mic Input Jack
No Connection
Table 1 - *See Wiring Instructions
Form SPA-400-IS, Rev.D