Description: Apple IIe: Video Signal "NTSC-Compatible", Not "NTSC-Compliant"
Header: Apple IIe: Video Signal "NTSC-Compatible", Not "NTSC-Compliant"


 This article last reviewed: 8 May 1990

 TOPIC -----------------------------------------------------------

 I bought Sharp XA305 video recorders to record the video from my Apple IIe
 systems: however, I am able to record only black and white pictures.

 I tried the same setup with an older Sears model VCR and it worked perfectly.
 I tried a new camcorder and got only black and white pictures again.  Sharp
 told me that this is because the Apple IIe has a substandard NTSC signal.

 Can you help?

 DISCUSSION ------------------------------------------------------

 The composite video signal coming from the Apple IIe is not stated to be an
 NTSC-compliant signal.  The signal coming from the video-out port is only
 considered NTSC-compatible video.  "Compatible" means that generally the Apple
 IIe video will work with an NTSC device, although it may not work in all
 situations.  Specifically, the Apple IIe video signal should work with all
 NTSC
 display devices.

 When the Apple II was first designed, economy was of great importance.  The
 video circuitry was built with as few parts as possible.  In the design
 process, it was discovered that certain portions of the NTSC broadcast
 specification could be omitted, yet still display a color image on a standard
 television set.  The one element that affects the described situation is color
 burst.  The Apple IIe does not contain the color burst element of the NTSC
 video signal.  By modulating other portions of the video signal, the Apple IIe
 simulates this missing information and allows an image to be produced on a
 television.  To provide a consistent color video image for video tape, this
 color burst needs to be present.

 In summary, the Apple IIe composite video signal was designed for display
 proposes, not for videotaping purposes.  The Apple IIe composite signal is
 close to the NTSC specification and allows the video signal to be displayed on
 television screens.  This, however, does not indicate that the signal can be
 recorded.  Since the signal is similar to the full NTSC specification, video
 sometimes records properly on videotape with certain VCRs.  In other
 environments, the signal may not record at all.  The capability to record a
 monochrome image falls between these extremes.

 To have a true NTSC signal designed for videotaping, the Video Overlay Card is
 required.
 Copyright 1990 Apple Computer, Inc.
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