[GreenKeys] Are my mails getting through?

[Ed Sharpe Archivist for SMECC via GreenKeys]

Yes we  saw it  here  Ed Sharpe Archivist  for SMECC _www.smecc.org_ 
(http://www.smecc.org) 
 
 
In a message dated 8/27/2015 6:35:12 P.M. US Mountain Standard Time,  
drlegendre at gmail.com writes:

I sent the following text yesterday, and surprisingly, it met no  reply. 
Another member says it never showed up in his inbox.  


Did it make it to the list?


-----ORIGINAL TEXT FOLLOWS----



Howdy Gents,


I'm just  completing a scratch-build of an RS-232 / 60mA CL converter 
device as  described on this page: http://www.aetherltd.com/connecting.html  


What is the purpose of the Keyboard Loopback  terminals (pins 3 & 4) on 
connector J1?


Pin 4 is a copy of the KB output signal on Pin 5,  and Pin 3 is tied 
directly to the 120V DC supply, just downstream of the 2K  10W current-limiting 
resistor. 


As I see it, when the converter is connected, but  idle, the current loop 
will be closed which would pull both Pins 3 & 4  down to roughly 3.3V DC 
above ground. This is assuming a 55R selector coil.  When the loop opens, Pin 3 
will rise to the nominal 120V DC supply, and Pin 4  will.. I don't know.. 
float? Show some high-Z voltage? 


So what's it all about, anyway? As ever, thanks  in advance - your help is 
much appreciated.  


BTW - I used a very cheap & common 28V AC  control transformer for the 120V 
DC supply. Running a standard voltage  +tripler+ gives me almost exactly 
120 DC with (what seems to be) very  acceptable ripple at 60mA. I used 3X 
1000uF @ 200V caps, but I'm sure it could  be executed with caps of lesser value 
(and voltage as well). In fact, the ESR  of the large caps may actually be 
a detriment to the tripler circuit -  eh?


-Bill




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