www
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SigtronicS
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S
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U
ltra
S
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US-lac4
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US-lac6 i
ntercomS
P
age
11
SYSTEM OPERATION
The following describes how to use the UltraSound System as well
as adjust the UltraSound controls. It also explains exactly how the
UltraSound unit operates. This will allow you to easily set all unit
functions to your specific needs. If you are not familiar with the
UltraSound operation, perform the next few steps while the vehicle
is not in motion.
Headsets
Put on the headset(s) and position the boom mike close to the mouth,
as is the practice with a hand-held mike. For best voice clarity, the
headset microphone must be positioned to one side of the mouth
and ¼ inch from the lips. Turn the volume control on the headset
ear cup to maximum. Turn down for individual hearing needs if
necessary only after intercom and radio volumes have been set
correctly. (see below)
Intercom operation and adjustment can be performed by the
following procedure:
1. Turn the intercom SQUELCH control to the maximum clockwise
position. For best system performance set the intercom VOLUME
control as low as possible. On most systems this will be approx-
imately the 10 o’clock position. NOTE: the intercom volume
control only adjusts the volume of conversation between the
headsets inside the vehicle. It does not affect the level at which
you hear the dispatch radio. See “Radio Operation”. You should
now hear yourself and others on the intercom.
2. To adjust the Intercom SQUELCH for voice activated operation
(VOX), it is helpful to have some background noise (truck engine
or…). Turn intercom SQUELCH control all the way counter-clock-
wise. Now, without speaking, rotate the SQUELCH control clock-
wise until you hear the background noise in your headset. Next,
rotate it counter-clockwise in small amounts until the background
noise disappears. Finally, make small adjustments until your voice
triggers the unit at comfortable speaking levels. This procedure
is necessary because the squelch is a “Fast-on, Slow-off” system.
When you speak, your voice will be heard in the headsets but the
sound will cut off about a second after you stop speaking. Minor
readjustment of the squelch may be necessary if the background
noise level changes significantly (engine idling to cruise power
with siren on).
RADIO OPERATION
With the UltraSound System, your radios are heard through the
headsets as well. Adjust the volume level of the dispatch radios
in the headsets with the volume control on the radio as normal.
NOTE that the radio volume does not effect the intercom volume
and vise versa.
Transmitting (talking to dispatch) from the selected headset posi-
tions is possible on a one-at-a-time basis. For a typical UltraSound
installation the Driver, Officer, or for US-LAC6 Crew #4 positions
can transmit at any time simply by pressing the PTT switch for that
radio. The other positions cannot transmit on the radios. When one
position transmits, several things take place automatically:
— All headset microphones, except for the transmitting position,
are muted.
— The selected radio is put into transmit mode.
— The headset microphone audio (your voice) is sent to the
selected radio.
— Sidetone is generated and sent to your headphones.*
* Sidetone is a portion of the transmitted voice signal sent back
into your headset so that you can hear what you are saying while
transmitting. The intercom VOLUME control adjusts the volume level
of the sidetone that you hear in your headset. The other headsets
will also hear the transmission sidetone. Of course, when the PTT
switch is released, (stop transmitting) all functions return to normal,
instantly and automatically.
