Methods Of Printer Language Switching - HP Color LaserJet 5500 Technical Reference Manual

Methods of Printer
Language
Switching
4-8 Kernel Commands
There are three methods of switching printer languages,
two of which are supported by all PJL printers. All three
methods are described below:
Explicit Switching. With explicit switching, the
ENTER LANGUAGE command is used to "explicitly"
select the desired printer language. This is the preferred
switching method because it ensures that the specified
printer language is always selected (see Figure 4-1).
Implicit Switching. If the printer has a default printer
language configured, and the print job does not explicitly
select a printer language using the ENTER LANGUAGE
command, the printer automatically switches to the
default printer language. (See the User's Manual for
each printer for instructions about specifying a default
printer language.) This switching method does not
always ensure that the proper printer language is used,
since the printer simply uses the default language.
Context Switching (HP Color LaserJet, LaserJet 4,
4M, 4 Plus, 4M Plus, 4Si, 4SiMx, 4000 series, 5Si,
5SiMx, 5Si Mopier, 4ML, 4P, 4MP, 4V, 4MV, 5P, 6P, 6MP,
DesignJet plotters and printers only). If the printer is set
to automatically select a printer language (see the
printer user's manual), and the print job does not
explicitly select a printer language using the ENTER
LANGUAGE command, the printer samples the
incoming data and looks for indications of a particular
printer language. Once it recognizes the printer
language, the printer backs up to the beginning of the
sampled print data and switches to the printer language
determined to be most appropriate. Then it begins to
parse the data in the newly selected printer language.
Note
HP LaserJet 4V and 4MV printers cannot properly
context-switch into the ESC/P personality by sensing the
data stream. Developers who use ESC/P must use explicit
or implicit switching.