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Two questions

Discussion in 'General Electronics' started by KellyClarksonTV, Jul 18, 2004.

  1. First, why is the record button on a tape recorder always Red? Does it have any
    significant meaning?

    Also, why does the play button also get activated when you push record? I
    actually looked inside to see what happenes when you push play and then when
    you push record. The record process has an extra square-shaped object comming
    down on the tape (persumably to record), but the play head is a few cm's down
    from the recording head. Wouldn't this cause echos?
     
  2. Rich Grise

    Rich Grise Guest

    It's easier to see.
    The other head is the erase head. The play head is actually the record/play
    head. It uses all the same stuff, except in record, the erase head is
    erasing, and the input and output of the amplifier are swapped.
     
  3. Mark

    Mark Guest

    To warn the user that they're about to erase anything
    existing on the tape.--
    Mark

    The truth as I perceive it to be.
    Your perception may be different.

    Triple Z is spam control.
     
  4. actually, I also wanted to know, is it possible to recover something you
    recorded over?
     
  5. Rich Grise

    Rich Grise Guest

    I don't know - why don't you give it a try, and let us know?
     
  6. I doubt it ... because if material could be recovered from an erased tape, you
    could hold lots (possible infinite) of information on a tape, since everytime
    you needed something, you would "unerase" it. If this technology existed,
    businesses would profit a lot by designing data storage devices that used this
    principle. But how about if the tape was erased just once and recently? Is it
    possible?
     
  7. Julie

    Julie Guest

    Yes.
     
  8. Then how?

    If not possible, it's scary, because all it takes is a soft push of the record
    button on your remote control and your wedding on video could be gone forever.

    When I was a 4th grader or so I used to compulsively worry about accidentally
    pushing record. I'd have to double check every night before I go to bed, after
    rewinding something, before leaving for school, etc ...
     
  9. Guest


    You sure that wasn't your only compulsion, considering the other posts
    about blowing things up? :}

    It is possible to recover some data from linearly recorded tapes as
    the recorded segment may not be aligned perfectly with the erase head
    or the record head alignment might be a little different. You'd need
    FBI/NSA level of expertise and equipment to pull this off though.

    -Chris
     
  10. Julie

    Julie Guest

    Chris answered pretty much what I what I know about it. The restoration is
    highly lossy at best.
    That is the main reason that recordable media such as video tapes have a 'write
    protect tab' to prevent just such occurrences. Now all you have to worry about
    is keeping your exploding batteries away from your tapes...
    ?!
     
  11. Karl Uppiano

    Karl Uppiano Guest

    Not likely. The erase head saturates the tape with a strong ultrasonic AC
    signal, meaning that the tape is alternately magnetized as far as possible
    in one direction, then the other. All usable signals are recorded at less
    than this level, so they are effectively obliterated. The same thing happens
    if a tape is "bulk" erased. In that case, the tape is brought into a strong
    alternating magnetic field that does the same thing as the erase head, only
    to the entire tape pack.
     
  12. but I've seen TV shows where the FBI recovered deleted files from computers.
    Isn't that the same concept?
     
  13. Sporkman

    Sporkman Guest

    NOT same concept. An "erased" file on a disk is actually not
    necessarily written over. It's just that it's place-marker in the file
    allocation table (FAT -- like a table of contents) is deleted so the
    system doesn't know it's there or where to find it any more. The space
    on the hard drive is then open for writing, whether or not anything has
    actually been written to it. Therefore the data MAY be available for
    recovery, although the chances for recovery are reduced over time by the
    probability of new data being written. With magnetic tape the erase
    head actually does overwrite (erase) what's there, allowing the record
    head to almost immediately write new information to the same spot.

    'Sporky'
     
  14. JeffM

    JeffM Guest

    I've seen TV shows where the FBI recovered deleted files from computers.
    Not deleted--altered. In the case of M$ OSes,
    the 1st character is changed to a lowercase rho (ASCII 229).
    The OS is designed to ignore these names.
    Yes. File recovery utilities, however, recognize the altered names.
     
  15. Sporkman

    Sporkman Guest

    Quite right and I defer to your better explanation.
     
  16. One major difference AFAIK is, that there is no erase head on
    harddisks, and thus, even if existing info is overwritten just once,
    some information (at the edges of the track) is still there and can
    be recovered with special equipment.
     
  17. Robert Baer

    Robert Baer Guest

    "Triple Z is spam control." - Does that mean that if i go to sleep,
    that i will get no spam?
     
  18. Charles Jean

    Charles Jean Guest

    ---

    OP should Google for the program Eraser.exe. Its a free download, and
    has the ability to do a DOD "government wipe" of all free area on the
    disk, including the un-overwritten file "feathers" you mention. Takes
    a while, though.
    If God hadn't intended us to eat animals,
    He wouldn't have made them out of MEAT!
    - John Cleese
     
  19. Mark

    Mark Guest

    Why don't you try it and tell us if it works?

    --
    Mark

    The truth as I perceive it to be.
    Your perception may be different.

    Triple Z is spam control.
     
  20. Robert Baer

    Robert Baer Guest

    I tried the ZZZ's and the phone woke me up...
     
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