SCS PTC-IIex, Manual

Page: 47 / 220

5 PTC-Firmware
Delay-Spread: to ±8 msec can be coped with
Coding: High performance error correction code, “full-frame interleaved”,
rate/2 or rate 3/4
5.12 PACTOR Duplex and Data Transparency
To simplify the PACTOR operation mode, that means to ensure compatibility to many
mailbox and terminal programs made for Packet-Radio (PR) while using PACTOR, the
possibility of working without the usage of special control key sequences (e.g. <Ctrl> +
<Y>) had to be created. Programs written for PR do not know the commands for
changeover used in the half-duplex mode on shortwave, because PR reacts in the half-
duplex mode on the user interface more or less like full-duplex – a changeover does not
exit for PR.
To avoid changeover commands using PACTOR the PTC-II offers a CHANGEOVER-
automatism , the so called PACTOR Duplex.
The PACTOR duplex is activated with the new command
PDuplex
(refer to chapter
6.70 , page 67 ). The automatism works with the following relatively simple algorithm:
1. If the PTC-IIex is the information sending station ( ISS), that means controls the
keys, the PTC-II automatically executes a CHANGEOVER, if his transmission buffer
is empty (that means no data to be sent are available).
2. If the PTC-IIex is the information receiving station ( IRS), the PTC-II automatically
executes a BREAKIN, if the transmission buffer is not empty, that means that data for
transmission are available and the IRS state exists for at least 12 seconds.
This automatism causes a variety of conclusions during practical operation that have to be
mentioned, especially if the PTC-II with activated PACTOR Duplex has to work together
with a
conventional PACTOR system.
The general usage of the PACTOR Duplex mode is not recommended at the moment,
because especially
old PACTOR mailbox systems have problems with the unnecessarily
automatically executed changeover of the PDuplex-PTC. The conventional operation
control in the personal
Chat-QSO should only be switched to PACTOR Duplex mode, if
the QSO partner is familiar with what happens and will not be confused by the change-
overs of the PACTOR Duplex-PTC appearing accidentally.
The following distinctiveness exists for the PTC-IIex itself when switched to PACTOR
Duplex:
1. The CHANGEOVER bell is generally deactivated.
2. Open files for the PTC internal mailbox will not be closed by a CHANGEOVER any
more.
3. Mailbox access of users with PACTOR Duplex are executed correctly (the command
interpretor will not be closed as usual by a CHANGEOVER, but generally by a
Carriage Return ).
33