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SM41 Rev. 4.00
3.4
Function Controls
The controls located to the right of the display are 'Function' controls. These controls
access the radio functions most often used. Access to all other functions is via the
status lines (see section 3.8 for further details on 'Status Editing').
Main RX Volume Control
3.4.1
Main RX (Receive) Volume Control
Set this rotary control to the furthest counterclockwise position (past the 'Off' detent) to
turn 'off' the radio. Rotating it clockwise will turn 'on' the radio. To increase the volume
of the main receiver, turn this knob clockwise; to decrease the volume turn this knob
counterclockwise.
3.4.2
RX/TX Status Indicator
Next to the main RX volume control is a bi-color LED indicator that displays the RX
(Receive) status of the main receiver and the TX (Transmit) status of the radio. When
the radio is transmitting the LED will light green. When the main receiver receives a
signal, the LED will light amber. If the radio is idle (not receiving or transmitting), the
LED will be dark. The color-coding used for these functions corresponds to standard
aircraft FM radio conventions. It is worth noting that this is the reverse of standard
vehicular conventions so may confuse some emergency services staff familiar with land
mobile equipment.
The receive indicator (amber) informs the operator that the channel is active with radio
traffic of some kind. A radio that is receiving may still not produce any audio if the tones
present on the receive signal do not match the tones set in the radio. See section 3.9
for further details on how CTCSS tones work.
Nov 10, 2003
ENG-FORM: 806-0105.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
NPX138 Panel Mount Radio Manual
RX/TX Status Indicator
Amendment # 4
Scan/Guard TX
Switch
Guard
Controls
Page 3-3
Jun 10, 2005
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