[GreenKeys] Stunt box

[epvgk at limpoc.com]

On Fri, Aug 19, 2011 at 09:46:58PM -0700, John Nagle wrote:
> On 8/19/2011 4:58 PM, greenkeys-request at mailman.qth.net wrote:
> > Hi again,
> >>  ?
> >>  I have been wondering just what a "stunt box" is and how it is used. From
> >>  what I have gathered, it is a mechanical device that is driven by the main
> >>  motor in a 28, and responds to certain signals coming through the loop. ?
> >>  I would love to know more about this, what it could do, how it was used,
> >>  and if there are any left in the collector world. ?
> >>  Thanks again!
> >>  ?
> >>  Joe
> 
>     It's a mechanical implementation of a state machine parser.
> It parses incoming character streams, looking for short
> sequences of matches.  The output can be sent to any of
> a Teletype's mechanical functions, or to electrical contacts
> for external functions.
> 
> 					John Nagle

It took a bit of observation to discover that mine was configured trip the
motor relay off when it received FIGS, NULL, A or something like that, which
I gather was a common use of the stuntbox, so that the machine could be 
powered off remotely. The motor relay would also be wired to trip back on
when the loop current was interrupted, as by someone sending it a character
or a break. 

Took me a bit of observation, experimentation, and profanity to get mine 
actually working that way. Sadly it's still not quite right - every few times
you send it the power off sequence, the relay clicks but it powers itself
right back on, so it's not dependable enough to really use. 

eric


> 
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