[GreenKeys] b&b electronics model 232tsopin

[epvgk at limpoc.com]

On Sat, Jul 02, 2011 at 07:06:26PM -0500, Randy and Sherry Guttery wrote:
> On 7/2/2011 6:12 PM, Adrian Stoness wrote:
> > anyone know anything about these things can't find any info apears to be
> > able to do searial loop not sure though like to figure it out befor
> > i accendently destroy it trying to conect it to my pc
> >
> > see photo>>  http://img97.imageshack.us/img97/3653/232tsopin.jpg
> Nope - not that specific device.  Appears to be an older 
> "legacy" B&B product - best bet is to email them and ask.
> 
> A few observations:  The optos are HP 6N135 - good for 
> around 20V @ 25ma - though they can pushed to near 30V - and 
> be run at near twice the current - depending on duty cycle.  
> They would probably be good to interface a later 20ma tty - 
> or *maybe* a really well running 28 sourced from just under 
> 30V...  though the 28 would be happier on 60ma (at 30V).    
> Certainly would NOT key a "standard" (100V+) tty loop (most 
> 28s and earlier)...  the high voltage would eat it alive!
> 
> best!
> 

I have been using 6N139s to read from tty loops... the optocoupler of course
isn't rated for anything like the voltage/current on a 60ma loop, so I use
a pair of resistors to shunt off a bit of current to run the opto.. basically
a resistor in series with the loop sized so that the voltage drop across it
is in the right range, and then another resistor in series with the opto
input. This isn't a "real" solution because the resistors have to be sized 
to the particular loop voltage and current in question but it's fine as an
expedient, and cheap enough if you're just messing around. 

eric