ASR-33 differences

tony duell ard at
Thu Aug 27 05:38:51 CDT 2015

> If I recall correctly; weren't the "preferred" versions of the 33ASR
> for use where the reader was controlled by the computer the 3-position
> manual reader control models? Since the reader won't run unless the
> computer is asserting the reader control lines anyway, and with such
> hardware flow control XON/XOFF automatic control become redundant.

Over here most ASR33s were used as locally-connected (current loop) computer
terminals. Every one I've seen has been manual control (3 position reader control)
and had a reader control relay fitted. So it certainly can be done.

I agree that if you have the reader relay there is no need for the XON/XOFF control
too. I don't think it matters if you have it, but no worries if you don't.

In any case the reader control is electrical, in fact the reader is the only part of the 
ASR33 not to have a mechanical connection to any other unit. Reader control means
energising (or not) the trip magnet at the rear right of the typing unit. So if you have 
the XON/XOFF control and find it gets in the way, it should be trivial to bypass it. 


Christian M. Gauger-Cosgrove
Contact information available upon request.

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