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7K • Appendix C
Repeater CTCSS Decoder
CTCSS, or Continuous Tone-Controlled Squelch System, is a convenient
problem solver for those bands that are being crowded with repeaters in
various parts of the country. In addition, the controller allows CTCSS to be
used as a qualifier for the entry of DTMF commands to increase the security of
the repeater system. Well-known trademarked names for CTCSS include: PL
or Private Line™ (Motorola), Channel Guard™ (General Electric), and Call
Guard™ (Johnson). Your repeater may already have a CTCSS Decoder built
in, or you may wish to install one of the add-on boards readily available from a
number of sources. The TS-64, from Communications Specialists, Inc.,
Orange, CA, 1-800-854-0547,
device is crystal-controlled for stability, and allows switch selection of one of 64
CTCSS tone frequencies.
The CTCSS Decoder should be installed in your repeater receiver following the
instructions provided by the decoder manufacturer. The output from the
decoder is usually an open-collector transistor driver which is either low active
or high active. This signal should be connected to Pin #5 of J2 (the female
DB25S connector).
To check your installation:
• Measure the voltage at Pin #5 of J2 with the receiver, CTCSS decoder, and
controller powered up.
• The voltage should swing above and below the 2.1V threshold as an
incoming CTCSS tone is applied and removed.
You must also determine the sense of your CTCSS decoder output.
• Does the output go low or high when the correct CTDSS tone is received?
• If the output goes low when the tone is received and returns high when the
tone is removed, then place DIP Switch #4 in the ON (closed) position.
• If, however, the output goes high when the tone is received and returns low
when the tone is removed, the place DIP Switch #4 in the OFF (open)
position.
An additional feature of this controller is the ability to change the CTCSS
decoder's frequency remotely. To do so requires that you use a CTCSS
decoder that has jumper- or switch-selectable tones, not pot-adjusted (tunable)
tones.
• You must remove any CTCSS frequency selection jumpers or open any DIP
switches to allow the controller to control the frequency.
• Connect wires from the frequency selection sides of the jumpers or DIP
switches to the CTCSS Frequency pins on the controller (see page C-16,
connector J2).
• Connect jumper or switch #1 to CTCSS Frequency #1, jumper or switch #2
to CTCSS Frequency #2, and so on.
• The TS-64 will use all 6 CTCSS Frequency connections.
• Other CTCSS decoders, eg. the TS-32, will need only 5.
• By entering the proper commands, you can tell the controller to connect the
jumpers or throw the switches on the decoder to change the tone
frequency.
C-8
http://www.com-spec.com
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