Sony PCG-GR300 Manual

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Write-protecting Memory Stick media 
Memory Stick media is designed with a write-protect tab to protect valuable data from accidental erasure or overwriting.
Move the tab to the right or left to set or release write-protection. 
Write-protect off 
Data can be saved on the Memory Stick media. 
Write-protect on 
Data can be read from but not saved on the Memory Stick media. 
  Using the Write-protect tab 
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