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Phonevision was a project by Zenith Radio Company to create the world's first pay television system. "Phonevision" Time January 8, 1951 It was developed and first launched in Chicago, followed by further trials in New York City and Hartford, Connecticut.
In July 1953, Zenith was forced to shut down KS2XBS when WBBM-TV was moved from channel 4 to channel 2 by the Federal Communications Commission as a side effect of channel shuffling in Wisconsin. The KS2XBS station's transmitter was later donated to Chicago's first educational station, PBS member station WTTW (channel 11).
In 1954, Zenith resumed testing in the eastern United States (on WOR-TV in New York City, now WWOR-TV and licensed to nearby Secaucus, New Jersey) and later negotiated foreign contracts in Australia and New Zealand. It also broadcast for a short time in Connecticut. In spite of its failure to gain national success, a significant amount of publicity and advertising for Phonevision was created for a short time.
The Phonevision system was operational on station WUVN in Hartford, Connecticut, for at least five years, ending early in 1968. The station would run conventional (non-subscription) entertainment programming during the day as an "independent" and then switch to Phonevision-encoded programming in the evening.
The Theatre Owners of America called the service a monumental flop. However, according to then Zenith president Eugene F. McDonald, the service was a roaring success. "Report on Phonevision" Time June 4, 1951 Even though the three films initially available to the first 300 test households were more than two years old, only about 18 percent of Phonevision viewers had seen them at the movies, and 92 percent of Phonevision households reported that they would prefer to see films at home.
Decoding of the audio was done by a dual-conversion processor. The audio was first shifted up 31.5 kHz, and then shifted down 34.125 kHz, producing a net "downshift" of 2.625 kHz. 31.5 was double the horizontal sweep frequency of 15.750 kHz, and 34.125 kHz was × 15.750, giving a convenient frequency reference. The frequency tolerance was so tight that if encoded audio were recorded during a Phonevision broadcast, and then played back later into a homemade processor running on normal network programming, a slight frequency error could be detected in the restored audio. Also, when the station switched to local sync to run a local commercial, the frequency change could be heard.
One of the major limitations of the Phonevision system was that due to the delay line being switched in and out, color could not be broadcast, as the 3.58 MHz phase lock necessary for NTSC color broadcasting could not be held. This limitation contributed to the demise of the system, along with the FCC authorization of subscription programming in 1969.
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