On 2/8/22 15:49, Paul Koning via cctalk wrote:

The maintenance manual (on Bitsavers) speaks of a "read/write head" and has an 
illustration that shows one of the head elements with a "read/write coil".  So the 
implication is that (a) there isn't an erase head, and (b) the same head serves for read or write 
according to whether the coil is being driven or sensed.
Yes, that is right.
   Come to think of it, I think erase heads are an aspect of audio tapes, not 
relevant to computer tapes.

No, all 9-track drives that I know of have erase heads that erase the tape to a no-transitions state before it is written on.  This allows you to obliterate old data when writing a new record, and leave gaps between records.  Since DecTape was synchronized by clock and mark tracks, that was not needed.

Jon

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