NPX138N Series Panel Mount FM Transceiver
SM41 Installation and Operation Manual
Section 3 Rev: 1.00
Issue 4
Page 3-12
ENG-FORM: 806-0115.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
3.11
Tones{tc "1.4.9
Tones"}
3.11.1
General
The tone system used by the NPX138N radio is a Continuous Tone-Coded Squelch System (CTCSS), as
defined by an Electronic Industries Association (EIA) standard. The radio adds these tones to the normal
signal modulation (such as voice) to uniquely identify or select a particular radio or group of users.
More commonly, these tones are referred to as sub-audible tones. This is because the filtering action of
the radio eliminates them from the received audio. Therefore neither the sending nor receiving party will
hear them. These tones are also sometimes referred to as Private Line (PL) tones.
3.11.2
Tone Display and Selection
The NPX138N radio displays the tones for the selected channel on the last three positions (far right hand
side) of the RX and TX lines. Use the Channel Edit mode to select and store the appropriate tones for
each channel. The operator can set different tones for receive and transmit. Select ‘
−
’ if no tone is
required.
By editing the TONE DISP status line, the operator can configure the radio to display the tones using one
of four different methods. The four tone display modes are:
• Tone Frequency (FREQ):
This is the actual frequency of the tone, measured in Hertz (cycles/second). There are only three
digits available on the radio to display this data, so the radio truncates any decimal fraction on the
display (i.e. 103.5 Hz becomes 103). Although not displayed, the radio uses the exact frequency.
• EIA Codes (1-38):
This is a number from 1-38 that identifies the tone in sequential order from lowest (67.0 Hz) to highest
(250.3 Hz)
• Wulfsberg
Codes
(WCODES):
These are sequential shifted OCTAL codes based on the thumbwheel design of the Wulfsberg C-1000
control. Because they are missing numbers ending in 0 & 9, they can be confusing, especially to
those familiar with the straight sequential number of the EIA codes.
• Motorola
Codes
(MCODES):
These are alphanumeric codes that often appear in the land mobile business, especially if Motorola
equipment is used.
The document reference is online, please check the correspondence between the online documentation and the printed version.
