Hi-Fi TV Soundtracks (pre 1978) - Why?

[W.B.]

Originally Posted by Mi40793

The ‘big three’ networks used 5kHz telephone circuits for audio until ~1978 when ATT added FM subcarriers providing 15kHz audio. ATT used Farinon FM modulators above the video at about 5-5.5 MHz.

Quad tape audio at 15 ips would do 15 kHz.
16mm television film projectors, ~6 or 7 kHz (best I ever saw)
TV station audio transmitter, audio path, etc., 15 kHz, same as any FM radio station required.

Working at two networks, everything audio was kept as flat a response as possible, with agc and peak limiting at transmitters.

Between Jan. 26 and Feb. 26, 1978, from what I have read, was the period when the transition from the old 100 Hz-5 kHz telco audio to the diplexing system that allowed 50 Hz-15 kHz audio transmission was effected. Apparently the later date was when the old telco audio was shut off permanently.