[GreenKeys] Loop electronics - a request for assistance

[Don Robert House]

My friends,

I am somewhat puzzled by the lack of a specific ground/return point  
for connecting my Info-Tech M6000 to a high voltage loop supply and  
the selector magnets of my Teletype machines.  The Info-Tech M200F is  
easy because the manual calls out TWO specific pins and shows a  
diagram which includes the loop supply complete with polarity  
markings!  Cool.  I can do that super easy.

The M-6000 assumes I am up to snuff as a bachelor of electronics and  
I guess I was about 30 or 40 years ago.  But the descriptions are  
incomplete and there is no diagram.   They call out ONE pin as the Hi  
voltage loop keyer and NO SPECIFIC return path.

Here is what the manual shows:

APPENDIX  I
SERIAL PRINTER OUTPUT SELECTION

The M-6000 offers three different serial printer output levels:

J6-  4  Mil-188  Mark = +5V,  Space = -5V
J6-  5  RS-232 (EIA)  Mark =  -7V,  Space = +7V
J6-15  High voltage, open collector transistor for 20 or 60 mA.  
loops,  Mark = Low
Note:  Maximum open circuit voltage on this transistor is 175 V.D.C.  
maximum current is 70 mA. and must be current limited (underlined).

APPENDIX  II
J-6  PINOUTS  &  FUNCTIONS (15 pin D-sub connector)

Pin          Function
1              Handshake from computer
2              Data from computer
3              Data to computer
4              Serial printer output MIL-level
5              Serial printer output EIA-level
6              Auto-start output
7              Serial printer handshake
8              Auxiliary data input
9              Spare
10            Ground
11            Ground
12            Ground
13            Ground
14            Ground
15            Serial printer output (Loop Keyer)

I assume that voltage, current flow, and polarity are important but  
they are not called out in the manual, nor is the correct ground, or  
"return" as we telephone people call it.

Sadly I have the service manual for the M200F but only the owners  
manual for the M-6000.

If any of you can be of assistance please reply.

Many thanks,

Don

Don R. House K9TTY
drhouse at nadcomm.com