The AppleCD SC Plus was Apple Computer's second CD-ROM drive, a replacement for the AppleCD SC which was introduced in 1991. Identified as model number M3021, just like its predecessor, the AppleCD SC, it used a 1x Read Only Media CD-ROM drive. The Plus could read a CD with up to 750 MB of data over the 650 MB of the AppleCD SC. It had indicator lights, an eject button, mini-phone audio jack, volume knob, and the CD caddy drive on the front of the accessory. On the back there were two 50-pin Centronics SCSI connectors, audio RCA connectors, power input, and a power switch. The AppleCD SC Plus had only minor improvements over the AppleCD SC and it was relatively the same. Several other models were made, including the 150, 300, 300e, 300i Plus, 300e Plus, 600i, 600e Plus and 1200i ('e' representing an external drive, and 'i' representing internal; model number also represents data reading speed in KB/s). They all include two Centronics 50-pin SCSI ports, and require
mains power. ==References==