Sigtronics SPA-400 - Manual

The Sigtronics’ SPA-400 is a voice actuated intercom with “transmit through
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.
Squelch Control — Allows the setting of voice actuated (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. SOLO FLIGHTS — Since the intercom is not needed during solo flights, 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 intercom 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 Transcom 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. amplified dynamic or electret). (U93 plug compatible jacks can be
used in place of the jacks provided).
• Mic Jack Insulating Washers: 4 shoulder and 4 fl at.
• 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. Center punch each hole at cross lines. (The five holes are in straight line 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 Transcom 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 Transcom chassis.
4. Insert Transcom from rear of aircraft panel with appropriate arrow pointing
upwards.
(continued)
SPA-400 TSO INSTALLATION AND OPERATING INSTRUCTIONS
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Figure 2
Figure 3 Microphone Jack
Sigtronics Corporation
178 East Arrow Highway
San Dimas, CA 91773
Phone: (909) 305-9399
E-mail: [email protected]
Web Site: www.sigtronics.com
Figure 1