Sigtronics RES-601 Operating Instructions

Sigtronics ST-400 / ST-600 STEREOCOM Operating Instructions

INTERCOM OPERATION

The intercom portion of the Sigtronics Stereocom ST400 /
ST-600 system is voice actuated with “transmit through the
aircraft radio capability” using your push-to-talk switches.
Three controls are provided on the SPA units:

ON/OFF 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 Control - Allows the setting of VOX operation
of the intercom for variations in background noise levels and
differences in headset microphones.

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 the MUSIC ON/OFF switch to
“OFF” and the PILOT/ALL switch to “ALL”. Turn the SPA
ON/OFF switch to the “ON” position.

2. Turn the intercom SQuelch control to the maximum
clockwise position. 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 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 signicantly (such as from
taxi to take- off power conditions).

Radio Transmit Mode

When the SPA unit is “ON”, 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,
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 modication to the SPA unit will enable
it to simulate sidetone. (See the “SPA-400 / SPA-600 Sidetone
Modication” instructions under the “HELPFUL HINTS AND
TECHNICAL INFORMATION” section of the ST-400 / ST600
STEREOCOM INSTALLATION INSTRUCTIONS).

When the SPA is turned “OFF”, only the pilot can transmit
on the aircraft radio(s). Both pilot and co-pilot will hear the
aircraft radio(s). The passengers will also hear the aircraft
radio(s) if the PILOT/ALL switch is in the “ALL” mode. With
the SPA unit “OFF” you will not hear intercom and cannot
talk to the other headsets.

Solo Flights

Since the intercom is not needed during solo ights, it may
be turned “OFF”. The pilot will still hear the aircraft radio(s),
since this circuit is always active, and may transmit to ATC via
his headset and push-to-talk switch. The pilot can also listen
to music (interrupted only by aircraft radio trafc) by turning
“ON” the MUSIC ON/OFF switch.

Specialists in “SOUND” Management

178 East Arrow Highway, San Dimas, CA 91773 ( 909 ) 305-9399

Back-up

Stereo Headsets

If a problem is ever 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 SPA unit should be turned
“OFF” and you should unplug the pilots headset mic plug
from the mic jack. (Leave the headphone plug in for radio
reception).

MUSIC SWITCHER OPERATION

1. Turn the Switcher MUSIC ON/OFF switch to “ON”. Turn
stereo your music source on and adjust to suitable
listening level.

2. Select the PILOT or ALL position to suit switching mode
desired. See Mode Selection Table. The Pilot and Co-pilot
are automatically switched from the music source to the
aircraft VHF radio when a radio message is received or
transmitted and are switched back when the radio trafc
is completed. The music is also automatically switched
out while someone is talking on the intercom.

Mode Selection Table

PILOT / ALL

SWITCH

ALL OFF VHF and ICS VHF and ICS

ALL ON

PILOT OFF VHF and ICS Music Only

PILOT ON

VHF — Aircraft VHF Radio. ICS — Intercom Audio.

MUSIC

SWITCH

PILOT &

CO-PILOT

Music interrupted

by VHF and ICS

Music interrupted

by VHF and ICS

PASSENGERS

Music interrupted

by VHF and ICS

Music Only

Sigtronics stereo headsets are specically designed for the
aircraft high noise environment 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 hear 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 under the “WIRING
INSTRUCTIONS” section of the ST- 400 / ST- 600
STEREOCOM INSTALLATION INSTRUCTIONS.

Sigtronics Corporation

178 East Arrow Highway
San Dimas, CA 91773
Phone: [phone]
E-mail: [e-mail]
Web Site: www.sigtronics.com

1-12-2007 st400opr.pdf