Capacitance Electronic Disc

Star Trek II: The Wrath of Khan CED removed from its caddy

          The capacitance electronic disc (CED) was an early audio video medium aimed at home use. CED was developed and primarily sold by RCA. CED used a grooved carbon doped PVC disc similar to a phonograph record. Carbon was added to give the discs a conductive surface. CEDs are read by a needle with an electrode. The needle physically contacts the disc riding in the groove, but unlike the phonograph needle, the needle in the CED player uses conductance to read the peaks and valleys in the groove below. This is necessary due to the extremely high density of CEDs. CEDs have a density two orders of magnitude greater than a phonograph LP. The audio and video on a CED is all analog, but 77 bits of digital auxiliary information that includes frame number is stored on the disc to prevent debris from causing a groove to replay repeatedly (Prentiss, 27). The discs could be damaged by handling, so they were stored in caddies that are inserted into the player and removed leaving the disc in the player. CEDs were sold as SelectaVision Videodisc or simply Videodisc. The CED was introduced to the U.S. market in 1981.

Home Video forgotten

there is nothing more difficult to take in hand, more perilous to conduct, or more uncertain in its success, than to take the lead in the introduction of a new order of things. Because the innovator has for enemies all those who have done well under the old conditions, and lukewarm defenders in those who may do well under the new. (The Prince by Nicolo Machiavelli recounted in Memories of VideoDisc)

          The quote above was delivered by Dr. Jay J. Brandinger, the former RCA Division Vice President and general manager of VideoDisc operations, in the last CED produced, Memories of VideoDisc. This last CED was a commemorative disc given out to RCA employees at the end of CED production. Though ostentatious this quote proves both true and false in interesting ways. Dr. Brandinger goes on to refer to CED as a “radical breakthrough” as opposed to what he describes as the incremental advances of satellite TV, video cassette recorders, and two way cable TV. The CED was a medium that has some clear lineage with the phonograph record, but refined to an extreme. It is new and old. It however stands alone. Magnetic tapes would see many refinements and uses before and after VHS, and optical media would see a similar trajectory. CED would not. There was one other similar disc technology. VHD was a designed around the same period, but it was only ever sold for consumer use in Japan. CED was only ever sold in the U.S. and to a lesser extent Britain. Memories of Videodisc concludes with another quote “The world will little note nor long remember” from Abraham Lincoln’s Gettysburg Address. This was certainly not true of the Gettysburg Address, but it seems largely a statement of fact for the Videodisc.

RCA SelectaVision SFT-100 VideoDisc Player

Maintaining a Medium

            Mass produced recorded media are by virtue of mass production at least a little easier to preserve. CED brings a few elements to the table that may limit its longevity. First of all is the needle cartridge in the players themselves. These cartridges have not been produced for over twenty years, and since there has never been another medium that used the same kind of needles and cartridges as CED. As it currently stands the general recommendation for replacing worn out cartridges for some players has already turned to simply finding another player with a working cartridge as it is easier than finding a replacement cartridge (“Stylus Cartridge Replacement Guide”). Otherwise the players themselves are primarily manufactured from off the shelf components that could be easily replaced and should be available for the foreseeable future. Tom Howe who runs CEDmagic.com even provides belts for free if you send him a self-addressed stamped envelope (“Products Available…”).

          The discs are yet another matter. They are notably more fragile than most videocassettes and optical discs. If anything touches the disc itself it may be permanently damaged. They are also subject to damage from being stacked much like vinyl records, but unlike vinyl records they are not easily produced. With the phonograph both the recording and playback are similar processes involving a needle vibrating in a groove. It is simply a matter of whether the groove is vibrating the needle or the needle’s vibration is forming the groove. There is no simple solution for producing future CEDs or duplicating current ones. The work of preserving media like this, so that it can be experienced falls in line with Ernst’s view of the role of the media archaeologist as engineer (Parikka, 62). For Ernst Technological media artifacts have to work in order to be fully explored both: in that we must understand their workings and that we must also experience their functioning (Ernst).

Blevins, Joe. “RCA’s failed VideoDisc turns ordinary movies into glitchy masterpieces.” Avclub.com.

Ernst, Wolfgang. “Media Archaeology-As-Such: Occasional Thoughts on (Mes-)alliances with Archaeologies Proper.” 15-23.

Memories of VideoDisc. Reproduced at “Memories of VideoDisc.” CEDMagic.com. 1986.

Parikka, Jussi. “Operative Media Archaeology: Wolfgang Ernst’s Materialist Media Diagrammatics.” Theory, Culture & Society. 28.5 (2011): 52-74.

Prentiss, Stan. “Video 81: Disc Players Laserdisc vs. CED.” Popular Electronics. July 1981. 26-30.

“Products Available from CED Magic.” CEDMagic.com.

“Stylus Cartridge Replacement Guide.” CEDMagic.com.