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EIAJ MTS is amultichannel television sound standard created by theEIAJ.
Bilingual andstereo sound television programs started being broadcast in Japan in October 1978 using an "FM-FM" system originally developed by theNHK Technical Research Labs during 1962–1969. This system was modified and standardised by the EIAJ in January 1979. Television stations in Japan with capability for bilingual and stereo sound transmissions used the callsign JO**-TAM, where "TAM" denotes their audio FMmultiplex sub-carrier designation, until digital switchover toISDB-T in 2010–2012 which eventually rendered EIAJ MTS obsolete.
The originalSystem M TV standard has amonaural FM transmission at 4.5 MHz. For Japanese multichannel television sound a second channel, or sub-channel, is added to the original signal by using an FM sub-carrier at twice the line frequency (Fh, or 15374 Hz). In order to identify the different modes (mono,stereo, ordual sound) apilot tone is also added on an AM carrier at 3.5 times the line frequency. The pilot tone frequencies are 982.5 Hz for stereo and 922.5 Hz for dual sound. Contrary toZweikanalton these pilot tones are not coupled to the line frequency but were instead chosen to allow use of filters already employed in the Pocket Bellpager system.[1]
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