Sigtronics RES-601 Installation Instructions - Manual (Page 5)

End of Jumper to Move Move to this Pad
Figure 5
Mode Selection Table
PILOT/ ALL
SWITCH
MUSIC
SWITCH
PILOT & CO-
PILOT HEAR PASSENGERS
HEAR
All Off VHF and ICS VHF and ICS
All On
Music interrupted
by VHF & ICS
Music interrupted
by VHF & ICS
Pilot Off VHF and ICS Music Only
Pilot On
Music interrupted
by VHF & ICS
Music Only
VHF – Aircraft VHF Radio ICS – Intercom Audio
page 5
INSTALLATION CHECK-OUT AND
ADJUSTMENTS
After the system is installed, again check that the SPA and
RES unit chassis, jacks, and wiring harnesses are clear of
all aircraft operating controls and cause no interference with
them. Check out the Stereocom installation by following the
instructions:
Plug in all the headset mic and phone plugs into the
respective intercom jacks. Put on the pilot’s headset and
position the boom mic close to the mouth, as is the practice
with a hand-held mic. Voice clarity is best when the mic is at
one side of the mouth and 1/4” from the lips.
To assure that the aircraft radios, pilot’s headset, and PTT
switch are connected and functioning properly, turn the SPA
units ON/OFF switch to the “OFF” position. Turn the MUSIC
ON/OFF switch to “OFF” and the PILOT/ALL switch to “ALL”.
If applicable, set the aircraft audio panel to “Headphone”
position. Then turn on the aircraft radio(s) as usual, and
verify that the pilot can hear the radios and can transmit
using his push-to-talk switch and headset. Aircraft radio(s)
and audio panel should operate exactly as they did before
the Stereocom system was installed. Aircraft radio reception
should be heard in all headsets. There should be no intercom
between headsets with the SPA unit turned “OFF”.
Next turn the SPA unit ON/OFF switch “ON”. Set the
SPA volume control to mid-position. For now, turn the
SPA Squelch control full clockwise. Verify that all headset
positions can now intercom with each other, including the
passengers. Verify that both pilot and co-pilot can operate
the aircraft radio(s). In this mode all headsets on the intercom
will hear the aircraft radio(s).
It may be necessary at this time to adjust the SPA unit
transmit mic output to the aircraft radios. A small adjustable
potentiometer is provided inside the unit for this purpose. It
is accessible through a hole in the side of the SPA chassis.
It is marked “MOD. ADJ.”, and can be adjusted with a small
blade screw-driver. In the event of over modulation (garbled)
or reports of weak transmission’s over the aircraft radio, an
appropriate adjustment can be made. Clockwise rotation
increases the output level to the aircraft radio mic input.
Counter-clockwise rotation decreases modulation level.
This adjustment sometimes needs to be made after the initial
installation of the intercom or if a new radio is installed. (The
output is set for unity gain at Sigtronics)
To verify music operation, connect your music source
to the music input jack, if applicable. Turn on the music
source and set volume to low level. Next turn “ON” the
Stereocom MUSIC ON/OFF switch. When the aircraft radio
and intercom are quiet you will hear music in the headsets.
Adjust the music source volume to a comfortable level.
Verify that music is heard in all headsets and is interrupted
by intercom conversations. If everything checks out, refer to
the separate ST-400 / ST-600 STEREOCOM OPERATING
INSTRUCTIONS sheet for proper use and other operating
modes of the Sigtronics Stereocom system. If something
does not work as described, carefully go over the system
wiring again. If OK, refer to the following section for helpful
hints and solutions to common problems:
HELPFUL HINTS AND
TECHNICAL INFORMATION
SPA-400 / SPA-600 Sidetone Modifi cation
Most aircraft radios, when transmitting, provide what is called
“sidetone”. Without sidetone, you will not hear yourself or your
co-pilot transmit to ATC. This can be distracting, especially
during instruction, because no one on the intercom will
hear the outgoing transmission of the radio conversation.
Some aircraft radios, however, do not provide this function.
Also, some radios are designed to drive only one headset.
Therefore, if you have such a radio, the sidetone may be
extremely weak or non-existent.
If this is the case and the sidetone cannot be turned up in
the radio(s), a simple modifi cation can be performed within
the SPA unit to simulate sidetone. The SPA requires partial
disassembly to accomplish this modifi cation. First unplug
and remove the SPA unit from the aircraft. To disassemble
unit, carefully remove the three screws securing the bottom
cover. Remove the cover to expose the solder side of the
circuit board.
Unsolder the wire from the solder trace at the end closest to
the controls. Move the free end of the wire to the solder pad
as illustrated in Figure 5 and solder. Replace the cover and
the three screws to complete the modifi cation. Install the SPA
unit into the aircraft panel and plug in the cable.
With the unit modifi ed in this way, the intercom VOLume
control adjusts the level of the sidetone. Note, when
“OFF” the SPA unit will not provide sidetone even with this
modifi cation.