> On Feb 8, 2022, at 4:04 PM, Ron Pool via cctech <cctech@classiccmp.org> wrote:
>> So it sermsdectape heads are special. I don’t think Dec would have the 
>> desire to make them internally so they probably contractef with a company 
>> already set up to do that. Who were the big tape head manufacturers at that 
>> time? Does anyone know?
> A photo of the back of a TU56 DECtape head can be seen at 
> https://www.pdp8online.com/tu56/pics/head_label.shtml?small .
> The head has a label on it that reads:
>  Western Magnetics
>  Glendale Calif.
>  Record
>  7282
> I've never seen a TU56 in person and have no idea if they have separate read, 
> write, and erase heads or some other combo.  The "Record" notation on the 
> above head's label hints to me this might be a write head.
> I found that and other DECtape photos at 
> https://www.pdp8online.com/tu56/tu56.shtml .

This picture https://www.pdp8online.com/tu56/pics/TU56_front.shtml?large shows 
the tape path clearly.  There is just one head assembly that performs reading 
as well as writing.  I don't know what "Record" refers to; the numbers near it 
look vaguely like a date code though not the usual year and week number.

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.  Come to think of it, I think erase heads are an aspect of audio tapes, 
not relevant to computer tapes.


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