[GreenKeys] Low level TEMPEST teletype interfaces

[John Nagle]

> On Jun 26, 2009, at 12:07 AM, Bob McConnell wrote:
> 
>> Roy Morgan wrote:
>>> ... I have in storage a Model 28 that I think is set up for low   
>>> voltage/tempest operation.
>> Internally, the M28 still used 60 mA loops to the selector magnets.  
>> Tempest introduced an external circuit that was +/- 7 volts at less  
>> than 1 mA.
> 
> Thanks to all who have replied with personal experience and other lore  
> about the Tempest Model-28's.  As is my habit, I've archived all this  
> info and will dig it out once I unearth the unit I have (a KSR) from  
> storage.

For NSA background information on low level Teletype circuit operation, see

http://www.nsa.gov/public_info/_files/cryptologic_histories/history_comsec.pdf

This report from 1966 details how signals were intercepted from the inductive
kick in Teletype selector magnets, and how hard it was to stop that.

					John Nagle