Bilingual and stereo sound television programs started being
broadcast in Japan in October 1978 using a system developed by
NHK Technical Research Labs. This system was modified and
standardized by the EIAJ in January 1979. The original version M
TV standard has a monaural 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, or dual sound) a
pilot 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 to Zweikanalton these
pilot tones are not coupled to the line frequency but were
instead chosen to allow use of filters already employed in the
Pocket Bell pager system.1 - ^ Numaguchi, Yasutaka (December
1979). "Present Status of Multichannel-Sound Television
Broadcasting in Japan". IEEE Transactions