P
age
8
S
igtronicS
U
ltra
S
oUnd
US-lac4
and
US-lac6 i
ntercomS
www
.
SigtronicS
.
com
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 grounding straps.
If servicing the vehicle’s charging system is impractical, 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 eventually 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, however, 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 Ultra-
Sound 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 to
the equipment causing the noise. Contact the company that
makes the offending equipment for a recommendation on
the type of filter to use.
If something does not work as described, go back over the wiring
and correct before going on. If all is well, you can tighten all headset
jacks and secure all jack box covers with the supplied hardware.
Also, tighten and secure all PTT switches. On the UltraSound unit,
turn down the intercom VOLUME control to approximately the 10
o’clock position.
IV. RADIO HOOK UP
The connection of the UltraSound unit to the vehicle’s radio(s) should
be done by someone familiar with the radio(s) such as your radio
installer. Refer to the UltraSound Wiring Diagram - Figure 4 for
US-LAC4 units or Figure 5 for US-LAC6 units. Only the radio functions
are shown for the radio end of the UltraSound Radio Interface Cable.
Because the connector(s) used by radio manufacturers varies widely,
you will have to consult the radio manual or manufacturer for the
connector(s) and pin assignments used. Sigtronics has extensive radio
interface experience and can assist with any question you might have
concerning this or any other aspect of the UltraSound system. See our
installation hot line number located on the last page of this manual.
First plug J2 of the Radio 1 Interface Cable into P2 of the Intercom.
Then using the radio manuals and the UltraSound Wiring Diagram,
identify the correct signal wires or connector pins to attach the
respective UltraSound wires. For most radios, these connections
are at the back of the radio or radio control head. For some radios,
the only place to connect the MIC HI and LO and PTT HI and LO
wires is to the hand-held microphone connector.* It is best to wire
in such a way that the radio hand microphone can still be used as
normal. Make sure that you do not physically tie the UltraSound
MIC LO and SPEAKER LO wires to the same pin on the radio, even
if they are tied together inside the radio. As in the headset wiring,
the connections between the UltraSound and radios should be
soldered and insulated for reliability. Do not use crimp type splices.
Use a good quality electrical tape or heat shrink tubing to cover the
soldered connections.
* For the more popular radios of this type Sigtronics manufactures plug
in “Y” adapters to make these connections easy. Contact your Sigtronics
dealer for pricing and availability.
For both US-LAC4 and US-LAC6 units, hook up Radio 1 first and test
before moving on to Radio 2.
Connect the six wires from the Radio 1 Interface Cable to the appro-
priate connections on the vehicle’s radio. Once that is done you will
need to set the RADIO 1 VOLUME switch on the back of the Ultra-
Sound unit. See Figure 6. This switch and the vehicles radio volume
control set how loud you hear the vehicles radio in the headsets.
For most applications the default setting of “LO” (up for Radio 1) is
fine. If the vehicles radio volume has to be turned up too high to
hear it in the headsets, set this switch to the “HI” position (down for
Radio 1). Otherwise leave it in the “LO” position. The switch can be
set with a pen or small flat blade screwdriver.
The last step is to set the Radio 1 Microphone Transmit Gain. Micro-
phone Transmit Gain (labeled MIC XMIT GAIN) adjustment for the
radio provided on the back of the UltraSound unit. The adjustment
sets the microphone audio level going to the radio during transmit.
The Microphone Transmit Gain adjustment will need to be initially
set to your particular radio. The gain once set, should never need
adjustment again unless the type of radio used is changed. The
following simple procedures take you through the adjustment of
the Microphone Transmit Gain.
Radio Microphone Transmit Gain Adjustment can be made
with a small, flat blade screwdriver. Referring to Figure 6, the gain
adjustment is set by two controls - a “HI/LO” RANGE switch and a
RADIO VOLUME switch for Radio 2
MIC XMIT GAIN RANGE switch for Radio 2
MIC XMIT GAIN ADJ for Radio 2
MIC XMIT GAIN ADJ for Radio 1
MIC XMIT GAIN RANGE switch for Radio 1
RADIO VOLUME switch for Radio 1
RADIO
VOLUME LO
HI
RADIO 2
RADIO 1
HI
LO
MIC
XMIT
RANGE
MIC XMIT
GAIN ADJ
*
FIGURE 6
