NPX138N Series Panel Mount FM Transceiver
SM41 Installation and Operation Manual
Section 3 Rev: 1.00
Issue 4
Page 3-5
The rotary knob independently sets the guard RX volume. In most models, there is no ‘Off’ detent
position. On most NPX138N models, even with the guard RX volume set completely counterclockwise,
the operator will still hear activity on the guard channel (at the preset minimum level).
The Guard Select switch (marked
GD1
/
GD2
on the faceplate) selects the active guard channel. For
standard guard receiver modules (-x5x), the first guard channel (GD1) has a receive frequency of
168.625 MHz and the second guard channel (GD2) has a receive frequency of 167.950 MHz, as specified
by the USFS. Radios with custom guard receiver modules are available (-x6x). For radios with
synthesized guard modules (-x7x), the receive frequencies for both the GD1 and GD2 channels are
programmable via the front panel or serial load to any frequency in the range of 138.000 to 173.995 MHz
in 5.0/6.25 kHz increments. The transmit frequencies of the guard channels are programmable. The
Guard RX LED indicator lights amber when there is activity on the selected guard channel.
3.7
General Controls — Normal Operating Mode{tc "1.4.5
General
Controls — Normal Operating Mode"}
Channel Switch
Brightness Switch
Edit Switch
Squelch Pushbutton
The General Controls are those labelled in the above diagram and affect the over-all operation of the
radio. The position of the
EDIT
switch determines the operating mode of the radio. The other three
controls (the two center-off momentary switches and the pushbutton) have dual functions, operating
differently depending upon the selected operating mode.
When the
EDIT
switch is in the center position (as shown), the radio is in ‘Normal’ operating mode and
the functions of the other switches are those of the upper label.
Lock the
EDIT
switch to either the left (
CH
) or right (
ST
) position, to set the radio in one of the two ‘EDIT’
modes. In both ‘EDIT’ modes, the functions of the other switches are those of the lower label. Engraved
panel lines tie related Edit functions together. See sections 3.9 and 3.10 for further details on editing.
3.7.1 Channel
Switch
To scroll to the desired channel use the
CHAN
switch. Momentarily press it to the right ‘
+
’ to increment
by one channel and to the left ‘
−
’ to decrement by one channel. Holding the switch in either the left or
right position causes the radio to continue to change channels with increasing speed. This allows for
quick selection of any channel.
Note
: Remote channel selection is possible with the installation of an external switch.
ENG-FORM: 806-0115.DOT
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