Sigtronics RES-601 Installation Instructions - Manual (Page 6)

page 6
1-17-2007 st400ins.pdf
Sigtronics Corporation
178 East Arrow Highway
San Dimas, CA 91773
Phone: (909) 305-9399
E-mail: [email protected]
Web Site: www.sigtronics.com
SPA-400 / SPA-600 ICS Load Modification
This modification is used when a SPA intercom is connected
to a radio or audio panel that has a low impedance headphone
output (less than 100 ohms). This is most common with some
Narco equipment (CP-135, CP-136, and Mark 12D, for
example) and “home made” audio select panels. Symptoms
are:
1. Intercom audio volume is weak or non-existent when the
SPA unit is in “ON” and ...
2. Transmit function is normal on aircraft radio and ...
3. Receive function is normal on aircraft radio.
Solution: Add a 1/4 or 1/2 watt resistor in-line with the BLUE
wire from pin 3 of J2. The value of the resistor most commonly
used is 220 ohms. However, optimum performance can be
achieved by selecting the value right for your particular
installation. The resistor can be any value between 100 and
330 ohms and is selected for the best balance between radio
receive volume and intercom volume.
Stereo Music Systems
Most automotive stereo units operate from 12V-14V sources.
Regulators or converters are available to permit operation
from 24V-28V sources.
Some FM receivers are capable of causing interference with
aircraft COM and NAV receivers. The aircraft panel should
be placarded accordingly. Most player only units (cassette or
CD) do not cause interference with aircraft receivers.
Stereo Headsets
The Sigtronics Stereocom systems are designed for use
with general aviation Stereo headsets with high impedance
speakers (300 to 600 ohms). Headsets with low impedance
(less than 100 ohms) speakers cannot be used with
Stereocom systems without modification. Contact Sigtronics
for details. In general, headsets with speakers of high and
low impedance and/or unmatched audio efficiencies should
not be used together without modifications.
Sigtronics manufactures stereo headsets specifically designed
for aircraft high noise environments and give excellent noise
attenuation. They also provide full frequency response stereo
for maximum enjoyment. They are compatible with aircraft
mic circuits and can be used as general aviation headsets in
aircraft that are not equipped with stereo headphone jacks.
This is because they include a switch to change from “Stereo”
to “Monaural”. No adapters required.
NOTE: General aviation headset (monaural) phone plugs
should not be plugged into Stereocom stereo phone jacks.
A monaural plug in a stereo jack shorts out one of the audio
channels and therefore renders the aircraft VHF radio and
intercom reception inoperative. (You may still here music,
however.) General aviation headsets may be used only if one
of the following three changes are made:
1. Monaural to stereo adapters are used on the headset
headphone plugs. (Only monaural music will be heard.)
2. The general aviation headsets are re-wired for stereo
reception.
3. Install the Sigtronics Stereocom system for monaural
operation. See note 10 on page 4 in the “WIRING
INSTRUCTIONS” section.
If something is still not right or you have any questions
regarding the installation and operation of the Sigtronics
Stereocom system or any other Sigtronics product feel free
to contact us directly. Technicians are available Monday
though Friday 8 am to 4:30 pm Pacific time.
This concludes the installation check-out. See the
separate ST-400 / ST-600 STEREOCOM OPERATING
INSTRUCTIONS sheet for complete Stereocom operation
information.