Sigtronics RMS-640 Operating Instructions - Manual

Sigtronics ST-440 / ST-640 STEREOCOM Operating Instructions
Specialists in “SOUND” Management
178 East Arrow Highway, San Dimas, CA 91773 ( 909 ) 305-9399
INTERCOM OPERATION
The intercom portion of the Sigtronics Stereocom ST440
/ ST-640 system is voice actuated (VOX) with “transmit
through the aircraft radio capability” using your push-to-talk
switches. Three controls are provided on the SAS units:
OFF/ALL/ISO Switch - Sets the intercom mode of
operation.
VOL - Volume Control - Controls the intercom volume. (Does
not affect aircraft radio volume. Set radio volume on radio
as normal).
SQ - Squelch Button - Automatically sets the VOX operation
of the intercom for variations in background noise levels and
differences in headset microphones.
Intercom operation and adjustment can be performed by
the following procedure:
CAUTION - As is standard practice with all aircraft avionics
equipment, be sure that the aircraft radio master switch is
turned off when you start up the aircraft engine.
1. With aircraft power on, set both the PILOT and PASS.
MUSIC ON/OFF switches to “OFF”.
2. Set the SAS OFF/ALL/ISO switch to the “ALL” position - the
preferred mode for setting the squelch. The SAS squelch
level can also be set with the SAS in the “ISO” mode, but
the pilot headset audio will not be utilized for squelch level
setting. For best system performance set the intercom
VOLume control as low as possible. On most systems this
will be approximately between 1/4 to 1/3 open. Note:
the intercom volume control only adjusts the volume of
conversation between the headsets inside the aircraft. It
does not affect the level at which you hear the aircraft
radio(s) or the level of the music. Notice the intercom is
now continually activated (hot mic mode) and you should
be able to talk between headsets.
3. To adjust the intercom squelch control for voice activated
operation (VOX), press and hold the “SQ” button down.
Now announce to the other persons in the aircraft not
to talk because you need a moment to set the intercom.
When all are silent release the “SQ” button. The intercom
will immediately go quiet. In approximately one second
the intercom will briefly pop on. This tells you the squelch
has finished automatically setting. If someone did speak
while the intercom was setting, it will have to be set again.
This is because the intercom would have tried to set to
a level just above the persons voice level instead of just
above the aircraft background noise level.
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.
In most aircraft, the squelch level wont need to be set again
until the next flight. In some high noise aircraft it is better to
set the squelch during climb or cruise.
Hot Mic Mode
When the SAS intercom turns on, it automatically comes
up in “hot mic” mode (non voice activated mode). During
a flight, if you want to deactivate the voice activated mode
and return to hot mic mode, simply turn the OFF/ALL/ISO
switch to “OFF” and wait 3 seconds and then turn it back to
“ALL” or “ISO”. To facilitate automatic setting of the squelch
level, whenever the “SO” button is held down, the intercom
also goes into hot mic mode.
Radio Transmit Mode
When the SAS is in the “ALL” mode, transmitting from both
pilot and co-pilot positions is possible on a one-at-a-time
basis. As normal, the pilot selects the appropriate radio he
wishes to use. When the pilot presses his PTT switch, his
headset mic is automatically routed through the intercom
to the radio. Only his mic will be live. The microphones of
the co-pilot and any passengers, will be muted when the
pilot transmits. Similarly in the “ALL” mode, when the co-
pilot transmits, only the co-pilots mic will go out on the
radio. When transmitting, the pilots will hear their own
voice via the aircraft radio sidetone return. (If the radio
does not provide transmit sidetone, then you will not
hear your voice. A minor modification to the SAS unit will
enable it to simulate sidetone. (See “SAS-440 / SAS-640
Sidetone Modification” section under the “HELPFUL HINTS
AND TECHNICAL INFORMATION” in the ST-440 / ST-640
STEREOCOM INSTALLATION INSTRUCTIONS). When the