Sigtronics US-12D - Manual (Page 7)

and PTT switches will also have to be soldered. See Figure 3
on page 4 for jack terminal identification.
We also do not recommend using screw type terminal strips
for intercom connections. There have been several instances
where terminal strips introduced high levels of electrical
noise like alternator whine into the intercom system. It is
acceptable however to tie the intercom red and green power
wires to existing vehicle terminal strips.
The best place to run the wiring between the unit and the
jack and PTT switches is out of sight. It should be run behind
vehicle panels and/or up in the headliner. This will reduce the
chance of personnel or equipment catching on or damag-
ing the wiring. Wire routing should take into account normal
vehicle operations. Wires should not interfere with any of the
vehicle’s controls, compartments, or doors. If the vehicle’s cab
tilts up for engine servicing, run wiring along the existing
vehicle wiring bundle. Make sure that wiring does not inter-
fere or restrict the tilting operation. Also, make sure that the
tilting operation will not cut or sever the wiring.
Make sure that the wiring does not rest on sharp edges. Over
time the vehicle’s vibration may cause a sharp edge to cut
into the wire. Use the provided wire grommets wherever
the four conductor wire goes through the hole into a jack
box. Use wire ties or tie wraps to secure and strain relieve
the wire.
At this time do not put the covers on the jack boxes or tighten
up the PTT switches. You will need to verify the correct opera-
tion of the system before you close everything up.
Power Connections:
The UltraSound unit will run on 11-16 VDC. CAUTION:
UltraSound units are designed for negative ground vehicles
only. They can be used on positive ground vehicles only if
a Sigtronics Positive Ground Adapter is used. Contact your
Sigtronics dealer on pricing and availability.
Make sure that the vehicle power is turned off before con-
necting the UltraSound power wire. The power for the
UltraSound unit comes in on the red and green wires on the
Headset Jack and PTT Switch Cable.
Connect the red wire to vehicle power. (Try not to use a power
buss that also runs electrical motors such as fans or light bars
with rotating lights.) Connect the green wire to the vehicle
chassis ground.
Intercom Wiring Check Out
System Setup:
Before you connect the vehicle’s radios, check out the system
operation. Do the following without the vehicle’s engine running:
First plug all headsets into the respective headset jacks. Put on
one of the headsets and position the boom mic close to the
mouth, as is the practice with hand-held microphones. Voice clar-
ity is best when the mic is about 1/4 inch away and slightly off
center from the lips. Turn the volume control on the headset, all
the way up (clockwise).
On the UltraSound unit, set both the intercom VOLUME con-
trol and SQUELCH control to full clockwise position.
Now turn vehicle power on. Verify that you can now hear
yourself in your headset. Verify also that you can hear all the
other headsets and that they can hear you. If everything is
OK, skip to the “PTT Test” on page 8. Otherwise, if something
is not working right, see the following troubleshooting guide
to find and fix the problem before going on with the instal-
lation:
NO INTERCOM IN ANY OF THE HEADSETS:
1. Make sure the UltraSound VOLUME and SQUELCH con-
trols are set to full clockwise position.
2. Make sure the vehicle power is on.
3. Check the in-line fuse in the UltraSound Headset Jack and
PTT switch Cable.
4. Check the power connection - red wire.
5. Check the ground connection - green wire.
6. Check for a short or open on the headphone wire (Blue
wire on the Headset Jack and PTT Switch Cable). The prob-
lem could be anywhere along the blue wire connection
between the headset jacks and the UltraSound unit.
INTERCOM IN SOME HEADSETS BUT NOT IN OTHERS:
1. Make sure that UltraSound controls are set as above.
2. Make sure that none of the PTT buttons are pressed.
3. Make sure that none of the PTT wires (white/red, white/
blue, yellow, or white/green if applicable) are shorted to
ground.
4. Check specific “bad” headset jack wiring for:
a) Microphone wire (jack ring terminal) open or shorted
to ground.
b) Headphone wire (jack tip wire) open or shorted to
ground.
c) Incorrect wiring - wires switched either at the jack or
at the point where the hookup wire connects to the
Headset Jack and PTT Switch Cable.
LOUD SQUEAL IN THE HEADSETS ALL THE TIME:
1. First make sure all headset plugs are plugged in all the way
and that no part of any headset jack is physically touching
any metal.
2. Check headset jack wiring at all jacks. For example, incor-
rect wiring such as reversing the jack tip and ring wires will
cause a squeal.
3. Check for open headset jack barrel connection (black wire).
The open could be anywhere along the black wire connec-
tion between the jack and the UltraSound unit.
4. Check for a microphone line (white/black, white/orange,
white/brown, orange, or tan wires) shorted to the head-
phone line (blue wire). The short could be at one of the
headset jacks or in the wiring between the unit and a
jack.
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