HP Color LaserJet 5500 Technical Reference Manual page 245

Timeouts
Backward-
Compatibility Mode
Printers that support the TIMEOUT variable:
HP LaserJet 4, 4M, 4 Plus, 4M Plus, 4V, 4MV, 4Si, 4SiMx,
4ML, 4P, 4MP, 4PJ, 4LJ Pro, 4LC, 4000 series, 5, 5M, 5P,
5MP, 6P, 6MP, 5Si, 5SiMx, 5Si Mopier
These printers have a timeout capability which is used to
recover when jobs are interrupted by situations such as
power failures. The timeout duration varies depending on
the data received by the printer.
The TIMEOUT variable set using PJL or the control panel
establishes the job timeout duration for those jobs that do
not contain JOB or ENTER commands. For jobs that do
contain the JOB or ENTER commands, the printer uses an
extended timeout duration, which is equal to five minutes
or ten times the TIMEOUT value, whichever is greatest.
Printers that support the backward-compatibility mode:
HP LaserJet 4, 4M, 4 Plus, 4M Plus, 4V, 4MV, 4Si, 4SiMx,
4L, 4ML, 4P, 4MP, 4PJ, 4LJ Pro, 4LC, 4000 series, 5, 5M,
5L, 5P, 5MP, 6L, 6P, 6MP, 5Si, 5SiMx, 5Si Mopier, HP
Color LaserJet, HP Color LaserJet 5, 5M
If the printer detects PCL data immediately after a job
boundary, it enters a backward-compatibility mode that
responds like an HP LaserJet III printer. This lasts
until the next job boundary is detected. For backward-
compatibility mode to occur, the PERSONALITY variable
must be set to AUTO or PCL, and the job must contain only
PCL data—if any PJL commands are received during the
job, the printer does not enter backward-compatibility mode.
Feature Support A-33