karn (05/17/82)
Does anybody know the technical details of the Mattel Playcable system? The local catv company is advertising it, and I'm curious as to just what is involved. I'm interested in carrier frequencies, bit rates, modulation techniques, protocols, etc. Phil Karn eagle!karn Bell Labs Murray Hill
mike@sri-unix (05/17/82)
Playcable is a joint venture between Mattel and the Jerrold Division of General Instrument. Jerrold makes cable tv components. Playcable is not two way cable as may be implied. You get a Mattel Intellivision and a cable adapter. The adapter plugs into the game instead of a game cartridge. You get a menu on the tv and you choose 1 of 30+ games. Meanwhile, each of these 30 games is passing by on the cable. When your game comes by, the adapter scoffs it up and loads it into the game (just like plugging in the cartridge). Playcable is being test marketed on the east coast and is not yet widely available. The response to Playcable has been tremendous, considering the cost of all those cartridges (and the game) versus a small monthly charge. Michael Wendel General Instrument Corporation Corporate Research and Development ucbvax!menlo70!sytek!gi!mike
karn (05/29/82)
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