Iscellaneous, Ettings, Dcs c – Motorola CT-39A User Manual

Page 57

FT-8800R Operating Manual

DCS C

ODE

NVERSION

The DCS system was first introduced in the commercial LMR (Land Mobile Radio) service,
where it is now in widespread use. DCS is sometime referred to by its different proprietary
names, such as DPL

(Digital Private Line

, a registered trademark of Motorola, Inc.).

DCS uses a codeword consisting of a 23-bit frame, transmitted (subaudible) at a data rate of
134.4 bps (bit/sec). Occasionally, signal inversion can result in the complement of a code to
be sent or received. This prevent receiver squelch from opening with DCS enabled, as the
decoded bit sequence would not match that selected for operation. Typical situations that
might cause inversion to occur are:

Connection of an external receiver preamplifier.
Operating through a repeater.
Connection of an external linear amplifier.

Note that code inversion does not mean that any of the above listed equipment is detective!

In certain amplifier configurations, the output signal (phase) is inverted from the input.
Small signal or power amplifiers having an odd number (1, 3, 5, etc.) of amplification stages
may result in inversion of a transmitted or received DCS code.

While under most circumstances this should not occur (amplifier designs and industry stan-
dards take this into account), if you find that your receiver squelch does not open when both
you and the other station are using a common DCS code, you or the other station (but not
both) can try the following:

1. Press the [SET] key momentarily to enter the Set mode.
2. Rotate the “Main” band DIAL knob to select Menu #11 (DCS.N/R).
3. Press the “Main” band DIAL knob momentarily, then rotate the “Main” band DIAL knob

to select the following mode.
TRX N

: Encoder; Normal, Decoder; Normal

RX R

: Encoder; Normal, Decoder; Reverse (Inverted)

TX R

: Encoder; Reverse (Inverted), Decoder; Normal

TRX R

: Encoder; Reverse (Inverted), Decoder; Reverse (Inverted)

4. Press and hold in the “Main” band DIAL knob for 1/2 second to exit to normal operation.

Remember to restore the default setting to “TRX N” (Encoder; Normal, Decoder; Normal)
when done.

ISCELLANEOUS

ETTINGS

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