[GreenKeys] Teletype Model 15 power Q's...

[WA5CAB at cs.com]

Not quite true.  The bit error rate with a single machine with the loop 
running on 12 VDC or even 24 VDC is quite large.  About the minimum loop supply 
voltage that can be expected to yield 100 % error free copy on a local loop 
is 48 VDC.  On a RATT circuit with only one receiving machine (selector 
magnet set) in the loop.  TD's and keyboards fortunately don't count.  There 
were very good reasons why all real TTY loop supplies are 115 to 130 VDC.  

In a message dated 11/08/2016 17:10:46 PM Central Standard Time, 
drlegendre at gmail.com writes: 
> Any M15 uses a 120V / 60ma DC current source to drive the communications 
> loop - some later models were selectable for 20mA loop. A 12-24V DC supply 
> (with some current limiting, possibly) should work for either in a "local 
> loop" or typewriter mode. 
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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