ignore terminal-to-terminal messages on telegraph
lines when using Telegraph Terminal Control Type I
(only). That is, a selected (polled) teletypewriter
station may address another teletypewriter station on
the same line without going through the 2703's pro
cessor and without causing channel interference due
to data
The
Terminal Control Type I lines.
two non-letters characters received from the line.
II the first such
and Device End status. If the first
ters comprise the sequence
own address), then
Channel End and Device End status.
If any other non-letters
the beginning of the message, the
the received data for
If this sequence is received, the
transferred to the processor, Timeout
set, and the command ends with Channel End,
Device End, and Unit Exception status.
not follow immediately because another station is being
addressed, tbe
Control Commands
Enable
is set within the line adapter of the addressed
communications line. No data transfer occurs. A
28-second timeout is initiated while waiting for the
line to become operational, except on a data set that
has automatic-answering capabilities.
Disable
'enable' latch
single byte to the channel from the sense field in the
byte defines the condition of the addressed communi
cations line.
This command is treated as a
and no operation is performed by the 2703. Channel
End and Device End are transferred in the status
byte. No access is made to the 2703 storage unless
the multiplexcr channel stacks the status response.
This command
The Reserve command is valid only when the Two
command is used to achieve attachment to the channel
via the
must be in a neutral state at this time.
ment to a channel is achieved, the Reserve command
is treated as an
Channel End and Device End status.
Release
This command is valid only when the
installed. If a Release command is issued by the
attached channel to any of the valid 2703 addresses
for that channel, and the command is honored, then
the
be command-free to honor this command.
Exception Commands
treated as an
These commands
programming compatibility between the 2702 and the
2703.
is automatically sent to the channel: (1) as a status