Sigtronics SPCC-3 - Manual (Page 4)

switches also have a female jack, it is not used.
The pilot should strap the switch end of his porta-
ble PTT switch to the yoke or stick of the aircraft.
The observer’s PTT can similarly be strapped to
the co-pilot controls or operated as a hand-held
switch. Various types of push-to-talk switches are
available from Sigtronics, including one that does
not have the female jack.
If you already have permanently wired push-to-
talk switches in the aircraft, and wish to use them
with the SPCC instead of the portable type, then
wiring modifications will have to be made to the
aircraft. Again, your avionics technician should
be able to do this for you.
6. Headset Hookup: All standard general aviation
headsets are compatible with the SPCC unit. He-
licopter type headsets can also be used if adapter
cables are used. (Sigtronics manufactures cables
that adapt the helicopter plugs to general avia-
tion plugs).
Plug the microphone and headphone plugs
on the headsets into the jacks labeled MIC and
HDPH, on the front panel of the SPCC. Put on
the headset, and position the boom mic close
to the mouth, as is the practice with hand-held
microphones. Voice clarity is best when the mic is
about 1/4” away and slightly off center from the
lips. Turn headset volume control(s), if any, all the
way up.
INITIAL SYSTEM CHECK-OUT
The following System Check-Out will provide you
with a “personalized” system. Perform the next few
steps while on the ground to assure that all func-
tions on the unit and radios are set to your personal
hearing and speaking comfort.
CAUTION - As is standard practice with all aircraft
equipment, be sure that the radio(s) and the SPCC
are turned OFF when you start up the aircraft engine.
1. To assure that the aircraft radios, and pilot’s
headset and PTT switch are connected and
functioning properly, put ON/BYPASS switch
into “BYPASS” position. Then turn on the air-
craft radios, and verify that the pilot can hear
the radios and can transmit using his push-
to-talk switch and headset. All other intercom
functions should be inoperable in the BYPASS
mode.
2. Intercom operation and adjustment can be
performed by the following procedure:
A. First set the ON/BYPASS switch to the “ON”
position and turn both REC VOL controls all
the way down (counterclockwise).
B. Turn both intercom volume controls to the 9
o’clock position and both squelch controls all
the way up (clockwise). Notice the intercom
is now continually activated and you should
be able to talk between headsets.
C. To adjust the intercom squelch controls for
voice activated operation (VOX), it is helpful
to have some background noise present. It
may also be necessary to turn up the inter-
com volume controls. Turn both intercom
squelch controls all the way counterclock-
wise. Now, without speaking, rotate one
of the squelch controls clockwise until you
hear the background noise in your headset.
Next, using that same control, rotate coun-
terclockwise small, incremental amounts
until the background noise disappears. (This
procedure is necessary because the squelch
is a “fast on, slow off” system). That squelch
control is now set.
D. Adjust the other intercom squelch control
similarly by turning it clockwise until you hear
background noise. Rotate counterclockwise
incremental amounts until the background
noise disappears.
Small adjustments may be necessary if air-
craft background noise changes significantly
- such as from idle to full power.
3. Radio Selection of both the aircraft and the FM
radios is provided by two switches.
A. XMIT SELECT determines the primary radio
you wish to transmit and receive on.
B. OFF/A/C, OFF/FM-1, OFF/FM-2 selects which
additional radio or radios you wish to receive
in your headset.
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