[GreenKeys] printing to KSR 28 was Re: OT: Radio Shack near bankruptcy

[epvgk at limpoc.com]

On Fri, Nov 14, 2014 at 08:26:07PM -0600, Jim Haynes wrote:
> I'm not familiar with the Black Box things being offered, but there
> is this caution.  Some 20/60 ma devices like Models 32, 33 and 35
> operate at low voltage, so the converter circuit is pretty simple.
> Models 15, 28, etc. normally operate with much higher voltage, so
> the converter has to be able to withstand the voltage.
> 
> We used to use bipolar transistors like MJE-340 but then the "sold
> state relay" chips became available, offering both high voltage and
> optical isolation.  I've attached someone's document on the subject;
> ask me by email if the attachment doesn't come through the system.
> 
> Jim W6JVE

Haha, I'm that someone. 
it's on my site at http://heepy.net


> 
> 
> jhhaynes at earthlink dot net


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