HP PCL/PJL reference - Printer Job Language Technical Reference Manual

A-60 Product-Specific Feature Support EN
5 The software may resume sending data after it sees the printer
go back online.
6 If the software does not detect the printer going offline and then
back online within 5 seconds of the echo, the application may
assume there is a printer error.
Paper Tray Configuration
The LaserJet 4000 and 5000 series paper tray configurations are set
up as follows:
Other trays are dynamically assigned at power-up, based on the tray's
number (for example, if you have a LaserJet 4000 or 5000 series
printer with an optional tray, tray 1 (MP tray) would be 0, the first
cassette number 2, the second cassette number 3, and the optional
cassette number 5 (number 4 is reserved for the envelope feeder).
Tray Number Description
0 Multi-purpose tray
1 Manual feed tray
2 Unknown tray
4 Envelope feeder
x Other trays (see below)