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noise, picked up by these jump seat headsets, can in some cases
produce excessive background noise in the intercom system.
Additionally, wide variations in engine noise (from idle to high
RPM) can falsely trigger the intercom VOX (voice activated)
feature. This is especially true for older vehicles with open jump
seats located next to the vehicle engine. There are two solutions
for this situation. The first one is the recommended one:
a) Order an additional Push-To-Talk (PTT) switch (and mount-
ing box if needed) for each open jump seat position. These
switches can be conveniently mounted at each jump seat
location and wired so that the jump seat headset microphone
is disabled until the switch is pressed. See Figure 2. The user
then presses his PTT button to talk on the intercom. PTT
buttons wired in this way only activate the intercom. They
do not let the jump seat locations talk on the vehicle radio(s).
b) Order Sigtronics headsets (Models SE-8P, SE-48P, or SE-18P)
with the intercom PTT switch already mounted on the ear cup
for the open jump seat positions. The user then presses the
PTT button on his headset ear cup to talk on the intercom.
The advantage of this method is that it eliminates having
to mount and wire in additional PTT buttons for the jump
seats. Note, however, most departments prefer to have all
the headsets on the vehicle(s) the same so that any headset
can be used in any position. The headsets with intercom PTT
switches on them cannot easily be used in a position that has
radio transmit capability such as the Driver or Officer position.
Sigtronics provides two ways to mount the headset jacks for the
UltraSound unit:
1. Mount the jacks in the supplied blue jack boxes.
Advantages:
a) Little or no “behind the panel” space required.
b) No vehicle panel thickness limitation.
c) No large holes are required to be drilled - a real advantage
on vehicles with thick metal panels.
d) Complete electrical isolation of the jacks from the vehicles
chassis, because the jack box is fabricated out of non con-
ductive high impact plastic.
2. Mount the jacks directly on the vehicle with a “through the panel”
mounting scheme. Advantages:
a) Smaller space requirement. (Only slightly larger than the jack
itself).
b) Only one hole to drill per jack ( ½ inch).
c) Most of jack is behind panel and out of the way.
Sigtronics recommends that you use the jack box mounting method,
but either approach can be used as well as a combination of both.
If required, additional headset jacks, PTT switches, mounting boxes,
and hardware are available through your Sigtronics dealer.
Splash Cover:
If a jack is to be mounted outside the vehicle (ie. on or near a fire
engines pump panel), a splash cover should be used to keep excess
moisture out of the jack when it is not in use. Every UltraSound
system comes with one such splash cover already pre-mounted on
a jack in a mounting box. On other positions, where the headset is
always plugged in, a splash cover is not required.
Jack Box Mounting:
Set the jack box on the mounting surface in the selected area and
mount with two of the hex head self drilling screws. For most appli-
cations* these screws can be installed with no pre drilling. Just power
in the screws with a standard electric driver with a 5⁄16 inch hex bit.
* No pre drilling required for aluminum and steel. A
1⁄8
inch pilot hole
will still be required with some stainless steels.
For most installations the wiring for the headset jack will come out
the back of the jack box. A hole is already provided in the jack box
for this purpose. Of course, you will also have to drill a similar hole
into the vehicle. Use a 5⁄16 inch drill for this.
Alternately, the wire can come out of the side of the jack box if
desired. You will have to drill the hole where required. Use a 5⁄16
inch drill. Rubber wire grommets are provided for the wire going
through the jack box hole.
Through the Panel Mounting:
For direct mounting of headset jacks on the vehicle panel you will
need to remove the jack from the jack box cover with a ½ inch
wrench. For normal jack mounting (no splash cover), the maximum
panel thickness is 0.10 inches or a little less than 1⁄8 of an inch. If you
need the splash cover (optional), the maximum panel thickness is
0.062 inches or 1⁄16 of an inch. NOTE: Longer headset jacks that can
accommodate thicker panels are available from your Sigtronics
dealer (order part number 100418 - maximum panel thickness 0.155
inches with splash cover and 0.195 inches without).
VOLUME
SQUELCH
INTERCOM
SEE TEXT
UltraSound
FIGURE 1
TAN
TIP
RING
BARREL
HEADSET JACK
INTERCOM PTT SWITCH
BLUE
BLACK
OPEN JUMP SEAT WIRING DIAGRAM
FIGURE 2
