Sigtronics SCI-S4 / SCI-S6 Operating Instructions
INTRODUCTION
This instruction sheet describes the operation of the Sigtronics
SCI-S4 / SCI-S6 intercom system. For information on SCIS4 / SCIS6 installation see the separate SCI-S4 / SCI-S6 INSTALLATION
INSTRUCTIONS.
The SCI-S series of aircraft intercoms incorporate voice activated
(VOX) intercom with “transmit through the aircraft radio capability”
using your push-to-transmit (PTT) switches. These systems include
three main modes of operation - ALL, ISO, and CREW. In addition
they allow for two separate Stereo music inputs one for the Crew
and one for the Passengers.
CONTROLS
Five controls are provided on the SCI-S units:
ALL/ISO/CREW Switch - Sets the intercom mode of operation.
PILOT/CO-PILOT VOL - Volume Control - Controls the intercom
volume for pilot (except in ISO mode when the pilot is switched off
the intercom) and co-pilot. (Does not affect aircraft radio volume.
Set radio volume on radio as normal.)
PILOT/CO-PILOT SQ - Squelch Control - Sets the pilot (except
in ISO mode) and co-pilot intercom turn-on threshold for voice
activated intercom (VOX) mode.
PASSENGER VOL - Volume Control - Controls the passenger
intercom volume. (Does not affect aircraft radio volume. Set radio
volume on radio as normal.)
PASSENGER SQ - Squelch Control - Sets the passenger intercom
turn-on threshold for voice activated intercom (VOX) mode.
SQUELCH INDICATOR LIGHTS - In addition the SCI-S units
provide two Squelch Indicator Lights - one for the Crew and one for
the Passengers. These lights show when the Crew or Passenger
intercom is active. These indicators greatly simplify the setting of
the intercom Squelch controls.
INTERCOM OPERATION
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.
SQUELCH SETTING - To use the SCI-S intercoms voice activated
(VOX) feature, the Crew and Passengers Squelch Controls will have
to be set. This can be performed by the following procedure:
1. To set the Squelch controls it is helpful to have some background
noise present and music sources off. With aircraft power on,
set the SCI-S ALL/ISO/CREW switch to the “ALL” position - the
preferred mode for setting the squelch. Turn both the SCI-S unit
volume (VOL) controls to the 10 o’clock position.
2. The Squelch controls are set one at a time. To set the Crew
VOX rst, turn the Crew Squelch (SQ) control full clockwise and
the Passenger Squelch control full counter-clockwise. Inform
everyone on the intercom to remain silent until you nish setting
the intercom squelch. Set the Crew VOX with the Crew Squelch
control and indicator light...
3. Turn the Squelch control all the way counter-clockwise. At this
point the corresponding squelch indicator light will be off. Now,
without speaking, rotate the Squelch control clockwise just
until you hear the background noise in your headset and the
squelch indicator light turns on. Next, rotate the Squelch counterclockwise a small amount and wait (approximately 1 second)
until the background noise disappears - squelch indicator off.
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. Now with
the Crew squelch set, repeat step 3 for the Passenger VOX with
the Passenger Squelch control and indicator light.
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 controls will not need to be set again
unless you change the number or type of headsets used with the
system. In some high noise aircraft it is better to set the squelch
during climb or cruise.
VOLUME SETTING - The Crew and Passenger Volume controls
should be set to minimum levels for best performance. Intercom
Volume levels set too high allows excessive background noise
into the headsets and promotes whispering into the headset
microphones. These combine to degrade what is called the “signal
to noise ratio” which decreases intelligibility and interferes with
proper Squelch (VOX) operation.
Specialists in “SOUND” Management
178 East Arrow Highway, San Dimas, CA 91773 ( 909 ) 305-9399
MUSIC OPERATION - Music is controlled at the music source
itself. To adjust the music volume level set the volume control on
the music source. Similarly, to turn on or off the music use the
appropriate control on the music source. When the music source is
“on” the SCI-S system automatically mutes and restores the music
to the headsets at the appropriate time depending on the mode.
The SCI-S default mode of operation is to partially mute during
intercom conversations and full mute during any aircraft radio
communications. See the SCI-S4 / SCI-S6 AUDIO PRIORITY
TABLE below for a more detailed operation listing.
INTERCOM OPTIONS
MUSIC MUTE LEVEL DURING ICS - During normal intercom
operation there is two possible muting levels, full or partial. This
level is user selectable prior to intercom installation. Note: during
radio transmission and reception, the music will always full mute.
This is for communication safety reasons.
SOLO FLIGHTS
Since the intercom is not needed during solo ights, it may be turned
to the “ISO” position. 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-transmit switch. If the aircraft radio does not
provide sidetone, then switch intercom mode to the CREW or ALL
mode. To hear music, the intercom will also have to be in the ALL
or CREW mode.
FAIL-SAFE
If power to the SCI-S unit fails, the pilot can still transmit and receive
on the aircraft radio(s) (assuming the radio(s) are still functioning).
Additionally, if a problem is ever suspected in the intercom, switch
to “ISO” mode or remove power to the unit. In this mode you will
still be able to transmit and receive on the aircraft radio(s) from the
pilot’s position. If the radio does not provide sidetone, then the pilot
will not hear his voice in the “FAIL-SAFE” or “ISO” mode.
PILOT TRANSMIT PRIORITY- When the pilot and the copilot press
their PTT switches at the same time one of two things will happen.
Only the pilot will go out over the radio, or both will go out over the
air. This is user selectable prior to intercom installation.
INTERCOM MODES
ALL MODE - When the SCI-S is in the “ALL” mode, transmitting
from both pilot and co-pilot positions is possible. 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
copilots mic will go out on the radio. Depending upon which priority
mode is selected, only the pilot or both will go out when both PTT
switches are pressed at the same time. When transmitting, everyone
on the intercom will hear the transmitting pilots voice via the SCI-S
sidetone return.
CREW MODE - When the SCI-S is in the “CREW” mode, transmitting
from both pilot and co-pilot positions are possible. 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 microphone of
the co-pilot will be muted when the pilot transmits. Similarly, when
the co-pilot transmits, only the co-pilots mic will go out on the radio.
Depending upon which priority mode is selected, only the pilot or
both will go out during simultaneous keying of the PTT switches.
When transmitting, the pilots will hear their own voice via the SCIS sidetone return. In this mode, the passengers will still have the
ability to intercom and listen to music among themselves and not be
bothered by radio trafc interruptions or crew intercom conversation.
Similarly, the pilots will not hear the passenger’s conversations.
ISO MODE - When the SCI-S is set to the “ISO” mode, only the
pilot can transmit and receive on the aircraft radio(s). The pilot will
not hear intercom or music and cannot talk to the other headsets.
The co-pilot and passengers still have intercom and music, but do
not hear the radios. If the radio does not provide transmit sidetone,
then the pilot will not hear his voice in the “ISO” mode.
SCI-S4 / SCI-S6 MODE SELECTION TABLE
MODE PILOT HEARS CO-PILOT HEARS PASSENGERS HEAR
ATC, Crew ICS, Pass ICS,
ALL
ISO ATC
CREW
Crew Music
ATC, Crew ICS,
Crew Music
ATC, Crew ICS, Pass ICS,
Crew Music
Co-pilot ICS, Pass ICS,
Crew Music
ATC, Crew ICS,
Crew Music
ATC, Crew ICS, Pass ICS,
Pass Music
Co-pilot ICS, Pass ICS,
Pass Music
Pass ICS,
Pass Music
SCI-S4 / SCI-S6 AUDIO PRIORIT Y TABLE
MODE ALL ISO CRE W
AUDIO AUDIO I S MUTED BY:
PILOT MI C Co- pilot PTT* Never Muted Co- pilot PT T*
CO- PILOT MIC Pilot PT T* Co-pil ot PTT Pilot P TT*
PASSENGE R MICS
PILOT
ATC RADI O
CO- PILOT
ATC RADI O
PASSENGE R
ATC RADI O
CREW MU SIC * *
PASS MUSI C **
Pilot PT T or
Co-pil ot PTT
Pilot PT T or
Co-pil ot PTT
Pilot PT T or
Co-pil ot PTT
Pilot PT T or
Co-pil ot PTT
Pilot PT T, Co- pilot
PTT, ATC, Crew ICS , or
Pass ICS
Pilot PT T, Co- pilot
PTT, ATC, Crew ICS , or
Pass ICS
Never Muted Never Muted
Never Muted
Always M uted
Always M uted Always M uted
Co-pil ot PTT, Co -p ilot
ICS, or Pa ss ICS
Co-pil ot PTT, Co -p ilot
ICS, or Pa ss ICS
Pilot PT T or
Co-pil ot PTT
Pilot PT T or
Co-pil ot PTT
Pilot PT T, Co- pilot
PTT, ATC, or Crew IC S
Passeng er ICS
NOTES:
ATC - Aircraft VHF Radio.
Crew - Pilot and Co-pilot.
ICS - Intercom Audio.
PTT - Push-To-Transmit Switch.
* Pilot Mic will always go out over the VHF radio when his PTT is
keyed. Co-pilot Mic will also go out when both PTT’s are pressed,
unless the “Pilot Transmit Priority” option is enabled.
** Music sources will partial mute on ICS, unless the “Full Music
Mute During ICS” option is enabled.
...when it counts!
Sigtronics Corporation
178 East Arrow Highway
San Dimas, Ca 91773
(909) 305-9399
www.sigtronics.com
scisoper.pdf SCI-S-OPER REV A 1-8-2007
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