TONE CODED SQUELCH
Yaesu FT-8800R Operating Manual (courtesy of W5JCK) Page 34 of 83
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 squelch from opening with DCS enabled, as the
decoded bit sequence would not match that selected for the operation.
Typical situations that might cause inversion to occur are: connection of an external receiver
preamplifier, operating through a repeater, and 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 the SET key momentarily to enter the Set mode.
2. Rotate the DIAL knob to select Menu #11 DCS.N/R.
3. Press the DIAL knob momentarily, then rotate the DIAL knob to select the
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 DIAL knob for ½ second to save the new setting and exit
to normal operation. 0.
Remember to restore the default setting to TRX N (Encoder; Normal,
Decoder; Normal) when done.
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