In the past there were owners manuals on e-bay for
these.
It is the first OTA pay TV system. IIRC the signal was
sent without the hoz sync & the audio on a second
channel. Decoding the audio gave the sync signal.
In Boston area we had 2 OTA pay TV's in the late 70's
One was a Zenith service from ch 27 in Worcester
( Wistah ) The other ch 68 Boston, used a same but
different method. Dont remember who built it, BT maybe ?
Anyhows the Zenith used a 9-151 module from a System 3
along with another board. No hoz sync, you got that from decoding
the "stereo" audio. The off air audio was the NWS from Worcester.
A Sanyo LM1800 IC was used by hackers. One pin
outputted the needed H sync.
Both featured skin flicks after 10 PM so quite popular !
73 Zeno