ASR-33 differences

Christian Gauger-Cosgrove captainkirk359 at
Wed Aug 26 21:35:17 CDT 2015

On 26 August 2015 at 14:03, tony duell <ard at> wrote:
> I've only ever seen the ones with 3 position levers, but from reading the
> manuals I think the 3 position levers are manual control models and
> 4 position levers are automatic control models (with extra levers and
> swtiches in the stunt box to start and stop the reader using XON/XOFF
> characters)
You are correct. The four position reader control lever are for
machines that use DC1/DC3 (XON/XOFF) to control the reader

> The 3 position lever models (manual control) can certainly take the reader
> run relay and be used with PDP8s and PDP11s.
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.

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

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