HP 24SII - Manual (Page 63)

The port select sequence may be sent as a separate ASCII file
preceding the print job, via DOS batch files, as part of a printer
initialization string, or by using the utility software.
%
A print job starts when the Model 24SII DES receives 3 or more
characters from a computer.
In Port Select Mode A (printer selection anytime), a print job is ended
when no characters are received by the Model 24SII DES from the
computer for the specified input inactivity timeout period or when the
computer sends a manual disconnect sequence.
In Port Select Mode A, when the Input Inactivity Timeout is set to 0
(zero) seconds, a print job is ended only under the following
conditions:
1) Manual Disconnect: Port Select Code followed by a terminating
character (Enter/Return or Line Feed).
2) Clear Buffer Command: Port Select Code followed by CLR and
a terminating character (see
Section 7.1.6 ).
3) Sending another Port Select Sequence: Port Select Code
followed by a module number, a port number, and a
terminating character. This will also start the next print job.