HP Color LaserJet 5500 Technical Reference Manual page 26

2-8 PJL Command Syntax and Format
Examples of invalid numeric variables include:
.123456
(The decimal point must be preceded by at least 1 digit)
-123.45.6
(Only 1 decimal point is allowed in a numeric variable)
+657,000
(Commas are not allowed in numeric variables)
Strings. Enclosed in quotation marks, strings consist of
any combination of characters from Roman-8 character
32 through 255, plus character 9 (horizontal tab),
excluding character 34 (quotation marks).
Examples of valid strings include:
"<HT>This is a valid string."
(Tabs are allowed in strings)
"Print job #4655"
Examples of invalid strings include:
"This is not a valid" string."
(Strings cannot contain quotation marks)
"This is also not<CR>valid."
(<CR> is not within the valid range of characters for a
string.)
Note
Strings displayed on the printer control panel are generally
displayed using the Roman-8 symbol set. On HP LaserJet
4PJ, 4V, and 4MV printers, when the language is set to
Japanese, strings which correspond to a control panel
message are displayed on the control panel using the
JIS X0201-76 character set.