Re: Consoles old and new

["Charles R. Fry" <Chucko%vermithrax.sch.symbolics.com@RELAY.CS.NET>]

    Date: Fri, 22 Sep 89 14:01 PDT
    From: Donald Leo Kaiser <dlk@bas-seatac.dialnet.symbolics.com>

    What does the PE stand for in "100MHz PE video signal"???

    Don Kaiser
    Boeing Advanced Systems
    dlk@faraday.bas-seatac.dialnet.symbolics.com

"Phase-Encoded".  Phase encoding (also called phase modulation) is a technique
similar to frequency modulation; it works by shifting the phase of a
constant-frequency carrier, such that a 0 can be represented as an unmodulated
carrier, and a 1 bit can be represented by a 90 degree phase shift.  (I do not
know what the exact modulation scheme is; these figures are examples only.)
The circuitry required is simple and (relatively) cheap.

Sending straight video signals through a long cable, especially
high-resolution monochrome signals, creates too much electrical noise; worse
yet, it's broadband noise, which requires too much shielding and filtering to
attenuate to the levels required by Federal Communications Commission
regulations.

By phase-encoding the video signal onto an 80 MHz (or 100 MHz) carrier, the
potential interference is confined to a smaller band, thus filtering and
shielding can be substantially simpler.  This more than makes up the cost of
the modulation and demodulation circuitry.

 -- Chuck Fry (Chucko@Riverside.SCRC.Symbolics.COM)
    Symbolics Software Support