SCS PTC-IIex, Manual

Page: 91 / 220

6 Commands
The fields mode and status have the following meaning:
Bit
2 1 0 STATUS-Bits Remark
0 0 0 ERROR
0 0 1 REQUEST
0 1 0 TRAFFIC
0 1 1 IDLE Idle byte in packet, does not exclude traffic bytes in
the packet!
1 0 0 OVER The system is busy with a CHANGEOVER. ERROR,
REQUEST, TRAFFIC, and IDLE are ignored.
1 0 1 PHASE AMTOR only.
1 1 0 SYNCH Active immediately after first half of a selcall or the
first 4 decoded PACTOR address bytes.
1 1 1 IGNORE Status currently not defined (e.g. STBY).
Table 6.3: PTC status information, Bit 0-2
Bit
6 5 4 MODE-Bits Remark
0 0 0 STANDBY
0 0 1 AMTOR-ARQ
0
1 0 PACTOR-ARQ Active no more than 20 ms after the end of the SYNC
sequence in the received SYNC packet, or for a
MASTER start no later than the begin of the data
packet.
0 1 1 AMTOR-FEC
1 0 0 PACTOR-FEC
1
0 1 RTTY / CW
1 1 0 LISTEN AMTOR or PACTOR.
1 1 1 Channel-Busy RF channel busy.
Table 6.4: PTC status information, Bit 4-6
In STBY condition the PTC-IIex analyzes the HF channel and differs between busy and
free . A busy channel is defined as all signals that are audibly distinctly different from
noise, but, however, having a speed < 250 Baud. Packet-Radio (300 Baud) is virtually
ignored. Furthermore, strong carriers on the channel are not evaluated as
channel busy .
Even the very hard to detect PACTOR-II signals were recognized. The PTC-IIex reacts
well even to short QPSK/BPSK sections, so that even the short PACTOR-II
acknowledgement signal is sufficient for the channel to be recognized as busy. This
function is essential for automatic stations, e.g.
WinLink
systems.
An occupied HF channel is indicated by a status value of 247 (Channel busy) being given
over the serial interface. After the PTC-IIex channel busy status has been activated, it
remains so for at least 3.5 seconds. An optical output is also given, with the TRAFFIC
LED lighting up when the channel is busy.
The Channel busy status is only given in the STBY condition, and not in Listen mode
(L=1)!
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