Compact disc
Compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony and released in 1982. The format was originally developed to store and play only sound recordings (CD-DA) but was later adapted for storage of data (CD-ROM). Several other formats were further derived from these, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video Compact Disc (VCD), Super Video Compact Disc (SVCD), Photo CD, PictureCD, CD-i, and Enhanced Music CD. The first commercially available audio CD player, the Sony CDP-101, was released October 1982 in Japan.
Pin insulator
Pin insulators have become collectible items. All glass pin insulators are assigned a Consolidated Design (CD) number, a system first implemented by hobbyist N.R. Woodward in 1954. Each CD number corresponds to a specific glass style, shape or manufacturer. Also, CD numbers are only hobby-specific for collectors, and are not used or recognised by insulator manufacturers.