[GreenKeys] Current limiting

[wa2hwj at att.net]

The 33 has a selector magnet driver circuit that keys the magnets
at 24 VDC at 500 ma.

Jack K0TTY




-------------- Original message from Chris Elmquist <chrise at pobox.com>: -------------- 


> I'm a little green on current loop fundamentals-- having grown up in 
> the RS232 age... but is the high voltage really neccessary if you are 
> not running a long distance with the loop? 
> 
> In other words, could a modern constant current source using say, LM317 
> be built that provides a nice stable 20 or 60mA but with only 12, 24 or 
> 48v DC source? 
> 
> Is there something in the older TTYs that requires a higher voltage on 
> the loop? 
> 
> My ASR-33 runs with 20mA sourced from 12v but that is pretty "modern" 
> compared to the 5-level stuff you guys are working with I am sure. 
> 
> Chris 
> -- 
> Chris Elmquist 
> mailto:chrise at pobox.com 
> _______________________________________________ 
> GreenKeys mailing list 
> GreenKeys at mailman.qth.net 
> http://mailman.qth.net/mailman/listinfo/greenkeys 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.qth.net/pipermail/greenkeys/attachments/20090120/8a52cfc4/attachment.html