From: utzoo!decvax!harpo!eagle!karn Newsgroups: net.video Title: Mattel PlayCable Article-I.D.: eagle.323 Posted: Fri May 28 23:39:58 1982 Received: Sun May 30 00:59:25 1982 I put a scope on the discriminator output of my FM tuner this evening and examined the PlayCable channels. (The signals from the receiver audio outputs were distorted and unusable, due to the high bit rate and the filtering of the stereo multiplex circuits). The modulation appears to be simple Manchester phase encoding, at a rate of 14,000 bits/sec. There is always a transition every 71.4 microseconds, and optionally one halfway between, depending on the data bit value. The FM deviation appears to be at least the full 75 khz that FM broadcast stations use. Any speculation as to the higher level protocols? (e.g., bit ordering, frame format, etc?) Phil Karn