Sigtronics UT-12D Installation And Operating Instructions Manual Download Page 3

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3. The location selected requires a minimum area of 2 5⁄16 inches

high by 7 7⁄8 inches wide by 4 inches deep. Verify that the intercom
unit and cables will not interfere with the normal operation of
any vehicle controls or the operation of vehicle compartment
doors.

Mounting Intercom Unit: See Figures 1 and 8

1. Once the location is selected, remove the mounting bracket

from the intercom unit by unscrewing the two large knobs. Be
careful not to lose any of the four ratchet washers.

2. Set the mounting bracket in the selected area and mount with

four of the hex head self drilling screws. For most applications*
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.

3. Place the intercom back into the bracket and replace the four

washers and two knobs. Set the Intercom to the desired angle
before tightening down the knobs.

II. HEADSET JACK AND PTT SWITCH INSTALLATION

Headset Jack Placement:

It is assumed that it has already been determined which positions
on the vehicle will have headsets. At this stage, it is helpful to have
a headset handy to physically gauge the best place for a particular
jack. There are several things to consider when selecting a place to
mount the headset jacks:

1. In general, for headset positions inside the vehicle, the jacks

should be placed towards the middle between the user’s posi-
tions. They should also be placed up above and towards the back
of the user’s head. This will assure that the headset cord will not
hang between the user and the vehicle door.

2. The headset jack should be out of the way so that the headset

plug can’t be hit during use or when entering or exiting the
vehicle.

3. The jack position should also take into account how the headset

cord will hang when the headset is in use. The cord should hang
out of the way and should not interfere with vehicle controls.

4. Verify that the jack placement and headset cable do not interfere

with the normal operation of vehicle doors or compartments.

5. In vehicles with intercom headset positions installed in open

jump seat locations, the combination of wind, road, and engine
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 below. 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 ST-8P, ST-48P, or ST-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 Passenger
position.

Sigtronics provides two ways to mount the headset jacks for the
UltraSound unit:

1. Mount the jacks in the supplied black 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.

VOLUME

SQUELCH

INTERCOM