through 2.35:1/CinemaScope, inclusive) which could be run without damage on any normal 35mm cinema projector. Nearly all original track negatives (OTNs) are now produced as stereo variable-area, and the former Western Electric (Westrex) system has been renamed Photophone and has become the de facto standard for analogue optical soundtracks, world-wide. The fully implemented case of stereo variable-area (i.e., 4-2-4 encoding/decoding) produces a stereo 3.1 track. The partially degenerate case of stereo variable-area (i.e., no 4-2-4 encoding/decoding, but discrete left total/left and right total/right) produces a stereo 2.0 track. The fully degenerate case of stereo variable-area (i.e., no 4-2-4 encoding/decoding, and left total/left equal to right total/right) produces a conventional "dual-bilateral" mono 1.0 track. RCA Photophone system abandoned – Westrex (stereo) variable-area system renamed Photophone Once the ability to record stereo tracks became a commercial imperative for sound-transfer facilities the RCA system was abandoned as it was incapable of producing time-aligned stereo sound negatives, whereas the Western Electric/Westrex recorders with the ca. 1938 4-ribbon light valve (RA-1231, e.g., but not RA-1231A) were inherently capable of producing time-aligned sound negatives. The Westrex system was renamed Photophone after the Western Electric and Westrex registered trademarks were sold by AT&T and Litton Industries, respectively, to others, for uses other than cinema sound systems. Renaming the Westrex system to Photophone was facilitated by the demise of RCA's cinema sound business unit, by the hand of General Electric, RCA's acquirer, and by its failure to protect the Photophone trademark. The Westrex system, briefly renamed Photophone, is still in use, with more than 100 systems currently in active service, world-wide. Some users, including Disney and Warner Bros., have multiple systems. The RCA system is essentially defunct. The Westrex system also has the capability of producing a DTS time-code track along with its native stereo variable-area tracks, or DTS time-code alone for use with 70mm and "special venue" prints. Photophone brand abandoned The re-use of the Photophone brand was relatively short-lived. After the closure of the immediate successor to Litton, the RA-1231 recorder and its supporting electronics were taken over by yet another successor. See also Joseph Tykociński-Tykociner List of film formats Movietone Pallophotophone Phonofilm Photokinema Sound film Sound-on-disc Vitaphone References Citations Bibliography Barrios, Richard. A Song in the Dark (London & New York: Oxford University Press, 1995) Coe, Brian. The History of Movie Photography (Westfield, NJ: Eastview Editions, 1981) Enticknap, Leo. Moving Image Technology: From Zoetrope to