Sigtronics Dual-CFR - Manual (Page 8)

page. If anything does not work as above, you have one of
three possible PTT switch wiring errors:
1. PTT line (white/red, white/blue, white/green or orange
wires) open or not connected between a PTT switch and
the UltraSound unit.
2. Open or missing return line (black wire) to a PTT switch.
3. Reversed PTT lines. The Drivers PTT line connected to the
Officer’s PTT switch and visa versa.
Electrical Noise Test:
The last thing to do before the radios are hooked up to the
unit is a simple noise test to verify system wiring as well as
vehicle electrical system integrity.
1. Unplug all intercom headsets except for the Drivers.
2. Make sure all the UltraSound panel controls and switches
are set as in “System Setup” on page 7.
3. Start the vehicles engine and let it idle a bit. This is a
stationary test — the vehicle should not be moving and
should be in “PARK” or “NEUTRAL” with brakes set.
4. Close all vehicle windows and doors to eliminate as much
background noise as possible.
5. Turn on as much vehicle electrical equipment as possible.
This usually means all lights and strobes. Do not turn on
sirens or horns.
6. Put on the Driver’s headset, position the mic, and make
sure the headset volume control is set to maximum.
7. With the vehicle still in “PARK” or “NEUTRAL” and brakes set,
slowly increase the vehicle engine rpm from idle to about
1500 RPM and back again. While doing this, listen for any
whine or hum in the headsets. Except for some possible
engine background noise being picked up from the head-
set microphone you should not hear any “Electrical” whine
or hum in the headset.
8. Shut off the vehicle engine as well as the lights, strobes,
etc. If, while the engine was running, there was no electrical
noise, skip down to “Radio Hook Up” on page 9. If you did
hear electrical noise, use the following to track down the
problem:
Turn the vehicle power off and disconnect the UltraSound
ground connection (green wire) from ground. Turn on the
vehicle power (engine off), put on the Driver’s headset and
see if the intercom part of the UltraSound unit is working.
IF YOU CAN HEAR YOURSELF IN THE HEADSET:
1. Then the UltraSound intercom return wire (black) is incor-
rectly grounded to the vehicle chassis. Look for:
a) A headset jack barrel touching the vehicle chassis. Most
common when a headset jack is mounted directly into
the vehicle’s panel without using the supplied insulat-
ing washers or incorrectly installing the washers.
b) The black wire pinched or cut and shorting to the vehi-
cle chassis. This can be anywhere along the intercom
wiring as the black wire goes to all headset jacks and
PTT switches.
2. Once the problem has been found and fixed, again make
sure that the intercom now does not work with the
green wire disconnected. You could have the black wire
grounded in more than one spot.
3. The next step is to reconnect the green wire and do the
electrical noise test again to assure that you have fixed all
possible noise problems.
IF YOU CANNOT HEAR YOURSELF IN THE HEADSET:
The intercom wiring is correct, but excessive electrical noise
from the vehicle’s power system is affecting the UltraSound
unit operation. This noise is getting into the unit on the
UltraSound power wires (red and green). There are basically
two types of power line electrical noise sources:
1. Noise generated directly by the vehicle’s electrical/ charg-
ing system — most commonly known as alternator whine.
This is only present when the vehicle’s engine is running
and recognized by the fact that the pitch or frequency of
the whine changes directly with the change in engine
rpm. (Higher frequency at higher engine rpm’s and lower
frequency at lower rpm’s.)
The preferred way to solve this type of problem is to have
the vehicle’s electrical / charging system serviced. The
most common cause of this type of noise is bad diodes
in the vehicle’s alternator. Other possible causes are: Bad
vehicle voltage regulator; Bad alternator or battery cable
connections; Missing or bad engine or alternator ground-
ing straps.
If servicing the vehicle’s charging system is impracti-
cal, installing a good alternator whine power line filter
between the vehicle power and the UltraSound red wire
will usually accomplish the same thing. Do not use the
type of filter that installs on or near the alternator. NOTE:
This solution should not be considered a permanent fix.
Vehicle charging system problems of this type will eventu-
ally cause other equipment failure as well as shorten the
life of the vehicle’s batteries.
2. The other type of noise is that generated by equipment
that uses the vehicle’s power. This type of noise is usually
constant and does not vary with engine rpm. It does, how-
ever, go away completely if the offending equipment is
shut off or disconnected. Electrical motors in fans or light
bars with rotating lights are two common examples.
Several things can be done to rectify this type of electrical
noise:
a) Find a better (less noisy) vehicle power source for the
UltraSound unit. Move the UltraSound red wire to
another power buss. Try not to use a power buss that
also runs electrical motors such as fans or light bars with
rotating lights.
b) Move the UltraSound ground connection (green wire)
to another ground point on the vehicle.
c) Install an electrical noise filter on the power line going
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