Sigtronics RES-400 - Manual (Page 4)

FINAL CHECKOUT AND ADJUSTMENT
After the unit is installed, again check that the SPA-400 intercom chassis,
RES-400 switcher chassis, jacks and wiring harness are clear of all air- craft operating controls and cause no interference with them. Check out
the system function by following the Operating Instructions.
SPA-400 INTERCOM OPERATING INSTRUCTIONS
I. INTERCOM MODE
A. Put on headset/s and position the boom mike close to the mouth,
as is the practice with a hand-held mike. Voice clarity is best when
mike is at one side of the mouth and ¼” 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. Set Music switch to “OFF” and Mode Switch to “ALL”.
E. Adjust Squelch Control clockwise to the point where ambient
background noise becomes audible. Then rotate counter clockwise a
very small amount and wait (approximately 1 second) for background
noise to diminish. Very small adjustments may be necessary it
aircraft background noise changes significantly (such as from taxi to
take-off power conditions). The above procedure is necessitated by
the fact that the squelch system is a fast attack/slow off system.
II. RADIO TRANSMIT MODE — Transmitting from both pilot and copilot
positions is possible on a one-at-a-time basis. The transmitting mike
disables all other mikes. 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.) If the radio does not
have side-tone, then you will not hear your voice.
(A minor modification to the Transcom will enable it to simulate side-
tone.)
It may be necessary at this time to adjust the Transcom mike output
to the aircraft radios. A small, square, adjustable trimmer potentio-
meter is provided inside the unit for this purpose. It is accessible
through a hole in the 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 mike 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.)
III. RADIO MONITORING — The aircraft radio is always heard with the
Transcom switched on or off to provide fail safe operation.
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,
and 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
oft. You will still receive the aircraft radio and will be able to transmit
from the pilot’s position. The hand mike may also be used, however,
the Transcom should be turned off and you should unplug your
boom mike from the intercom mike jack. (Leave headphone plugged
in for radio reception.)
RES-400 SWITCHER OPERATING INSTRUCTIONS
1. Turn Stereo Switcher and entertainment system “ON” and adjust
entertainment to suitable listening level.
2. Select Pilot or All position to suit switching mode desired,
3. Switching: Pilot and co-pilot are automatically switched from the
audio bus of the entertainment system to the VHF radio when a
radio message is received or transmitted and is switched back
when the radio traffic is completed.
4. Music is automatically switched OFF when voices are present on
the intercom.
5. See Mode Selection Table for additional switching options.
MODE SELECTION TABLE
Mode
Pilot/All
Switch
Music
On/Off
Switch
Pilot & Co-Pilot Hear Passengers Hear
PILOT ON VHF & CS Interrupt Music Music Only
ALL ON VHF & CS Interrupt Music VHF & CS Interrupt Music
PILOT OFF VHF & CS Only Music Only
ALL OFF VHF & CS Only VHF & CS Only
HELPFUL HINTS AND TECHNICAL INFORMATION
ENTERTAINMENT SYSTEMS: Stereo entertainment systems should
be used that have a common ground output (speaker) connection.
Systems that have a full floating output (two pair of speaker wires that
have directions not to tie speaker returns together) cannot be used
with stereo headphones or with the RES-400 without modifications.
Power: Most automotive stereo units operate from 12V-14V sources.
Regulators or converters are available to permit operation from 24V-
28V sources.
Portable stereo units may be used, however, minor modifications may
have to be made to the RES-400 unit; particularly if they have head-
phone outputs rather than speaker outputs.
Some automotive FM receivers are capable of causing interference
with aircraft COM and NAV receivers. The aircraft panel should be
placarded accordingly. Tape players (cassette or CD players) do not
cause interference with aircraft receivers.
STEREO HEADSETS: The Stereocom is designed for use with high
impedance receivers such as are in the Sigtronics headsets. If the
use of low impedance receiver headsets is contemplated, then modifi-
cations to them or the Stereocom will be necessary. Contact Sigtron-
ics for details. In general, headsets of high and low impedance
receivers and/or unmatched audio efficiencies should not be used to-
gether without modifications.
The Sigtronics stereo headsets were specifically designed for the aircraft
high noise environment and give excellent noise attenuation. They also
provide full frequency response for maximum stereo enjoyment. They are
compatible with aircraft mike circuits and can be used as a general
aviation headset (in aircraft that are not equipped with stereo headphone
jacks) by using a “stereo-to-monaural” adapter plug.
General aviation headsets may be used only if one of the following three
changes is made:
1. Monaural phone jacks are substituted for the stereo headphone jacks
provided. (Only monaural music will be heard.)
2. Monaural to stereo adapters are used on the headset headphone
plugs. (Only monaural music will be heard.)
3. The general aviation headsets are re-wired for stereo reception.
The VHF and intercom outputs will be short circuited and therefore
rendered inoperative if one of the above three changes is not made.
(General aviation headset phone plugs cannot be plugged into
Stereocom stereo phone jacks.)
Form ST-400, Rev. D