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DCS C
I
The DCS system was first introduced in the commercial LMR (Land Mobile Radio) ser-
vice, where it is now in widespread use. DCS is sometime referred to by its different
proprietary names, such as DPL
Inc.).
DCS uses a codeword consisting of a 23-bit frame, transmitted (sub audible) at a data rate
of 134.4 bps (bit/sec). Occasionally, signal inversion can result in the complement of a
code being 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 the
2. Rotate the DIAL knob to select Set Mode Item 27: DCS
INVERSION.
3. Press the
Mode Item.
4. Rotate the DIAL knob to select one of the following modes:
RX-NORMAL, TX-NORMAL:
Receive and transmit the Normal DCS Tone.
RX-INVERT, TX-NORMAL:
Receive the Inverted DCS Tone and transmit the Normal DCS Tone.
RX-BOTH, TX-NORMAL:
Receive both Normal and Inverted DCS Tones and transmit the Normal DCS
Tone.
RX-NORMAL, TX-INVERT:
Receive the Normal DCS Tone and transmit the Inverted DCS Tone.
VX-8DR/DE O
CTCSS/DCS/EPCS O
DCS O
®
(Digital Private Line
key for one second to enter the Set Mode.
key briefly to enable adjustment of this Set
M
®
, a registered trademark of Motorola,
PERATION
37
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