62
FT-7800R O
PERATING
M
ANUAL
M
ISCELLANEOUS
S
ETTINGS
DCS C
ODE
I
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 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 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 and hold in the [
BAND
(
SET
)] key for 1/2 second to enter the Set mode.
2. Rotate the
DIAL
knob to select Menu #10 (
DCS.N
/
R
).
3. Press the [
BAND
(
SET
)] key momentarily, then rotate
the
DIAL
knob to select the following mode.
T
/
RX N
: Encoder; Normal, Decoder; Normal
RX R
:
Encoder; Normal, Decoder; Reverse (Inverted)
TX R
:
Encoder; Reverse (Inverted), Decoder; Normal
T
/
RX R
: Encoder; Reverse (Inverted), Decoder; Reverse (Inverted)
4. Press the [
BAND
(
SET
)] key momentarily to save the new setting, then press and hold in
the [
BAND
(
SET
)] key for 1/2 second to exit to normal operation.
Remember to restore the default setting to “
T
/
RX N
” (Encoder; Normal, Decoder; Normal)
when done.
