Vaisala CT25K - Figure 4-2 Open and Closed Port

Ceilometer CT25K
User’s Guide CT25K-U059en-2.1
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CLOSED Measurement data message transmitting state. In this state messages
are transmitted automatically at predetermined intervals, or as a
response to a polling input string, depending on the corresponding
settings. User commands are not accepted, except command OPEN,
which turns the line into the OPEN state. No input is echoed but
ENTER inputs are responded to by character string CT:
OPEN User dialog state. In this state the user commands are responded to.
Command input is echoed. A command prompt CEILO> is
displayed as an indication of readiness for command input from the
user. Command line termination and command execution is by key
and character ENTER = RETURN = CARRIAGE RETURN. No
automatic measurement data message transmission is executed in
the OPEN state. The port reverts into the CLOSED state by
command CLOSE. Automatic 2-minute time-out after last character
input is applied. A 2...60-minute time-out may be set by command
SET PORT TIME_OUT.
NOTE
Only one of the ports can be OPEN for commands at a
time. Only one of the ports transmits measurement
messages at a time. Additionally, in RS-485 mode a unit
ID must be given with the command OPEN.
Figure 4-2 Open and closed port