A CD-ROM reader designed for network use.  It can be configured as a tower or jukebox.  Towers contain several drives, and each drive holds one CD-ROM.  Jukeboxes hold from a couple dozen to hundreds of discs, but have only a small number of drives.  A robotic mechanism moves the discs to the drives as required.  See 
CD-ROM changer.
CD-ROM Server
This is the transport mechanism of the Grundig GMS 3200 CD-ROM server.  It can hold up to 200 CD-ROMs and six drives.  (Image courtesy of Grundig Professional Electronics, GmbH.)