HP 8920A, User Manual

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Chapter 8, Signaling Decoder Screen
Continuous Digital Controlled Squelch System Decoder
Arm Meas
Arm measurement prepares the decoder to be triggered by an incoming signal
when
Single
is selected.
Code (oct)
This field displays all of the code word combinations from the received data
stream.
The top entry in this column is always 1 of the 83 standard (primary) industry
codes or
NPC
(No Primary Code). All other possible code combinations are listed
in numerical order after this entry.
If a Turn-Off Code (TOC) is measured for a full sampling period,
TOC
is
displayed with no other codes listed.
Data (bin)
This measurement field displays a 23-bit segment of the data stream being
received.
After 23 bits have been received, the decoder shifts the bit sequence 23 times until
all possible bit patterns have been analyzed. Any possible code words are
displayed in the
Codes (oct)
column. Even if no code words are found, this
field will still display the bit sequence that was received.
Operating Considerations
This field is blank if the only signal received during the decoder’s latest sampling
period is a turn-off-code.
The final bit pattern displayed will not necessarily match any of the displayed
codes, since the bits are shifted 23 times during decoding.
Data Rate
This measurement field displays the data rate in bits-per-second for the data
stream being received.
Operating Considerations
For accurate measurements, the
Data Rate
for the CDCSS encoder should be set
to the expected data rate for the signal being analyzed by the CDCSS decoder.