Compaq 247320-003 - Deskpro 4000 - 5166 Model 2500/CDS Reference Manual page 79

With the computer turned on, you can insert a disc by sliding the
disc into the slot on the front panel of the drive.
The drive performs a diagnostic check and automatically begins
reading the table of contents. The busy indicator turns amber
while the drive reads the table of contents.
The disc automatically ejects if the disc is upside down,
not properly aligned in the drive, or if any other condition
prevents the drive from reading the disc.
When the busy indicator turns amber, the drive is ready to
receive commands and data may be retrieved from the disc.
To remove the disc, press the eject button
of the drive. You must remove the disc before turning off power
to the computer.
on the front panel