Dell P1500 Personal Mono Laser Printer - Manual (Page 70)

What this light sequence means:
The printer has lost the connection to an external print server (also called an
external network adapter or ENA).
This light sequence is displayed if your printer is connected to the network,
but it cannot detect the print server when you turn on the printer.
What you can do:
Make sure the cable connecting the ENA and the printer is securely
attached. Turn the printer off and then on to reset the printer.
Press and hold Cancel to reset the printer.
Secondary error code
What this light sequence means:
The printer cannot establish communication with the network.
What you can do:
Press and release Continue to clear the message and continue printing (the
job may not print correctly).