DCS Code Inversion
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 prevents the receiver’s 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 defective!
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
standards 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 and hold in the [
MHz
(
SET
)] key for one second,
then rotate the
DIAL
knob to select “
15 DCS RV
”.
2. Press the [
MHz
(
SET
)] key momentarily, then rotate the
DIAL
knob to set this Set Mode Item to “
ENABLE
” (thus
inverting the DCS Code).
3. When you have made your selection, press and hold
the [
MHz
(
SET
)] key for one second to save the new set-
ting and exit to normal operation.
4. Remember to restore the default setting to “
DISABLE
” when done.
58
Miscellaneous Settings
FT-2980R Operating Manual
