DEC M3134-PA DS500 module

Jay West jwest at
Thu Apr 20 16:23:54 CDT 2006

Richard wrote....
>A module list I scrounged off the net says this:
> M3134-PA    DS500       Q   IBM Terminal server, 4 port (DECServer 500)

Let me say first that I am not at all familiar with the M3134. However, I 
think you're missing the basic concept here. The IBM coax terminals do not 
speak ascii, nor do they speak RS232. Nor are they character based like ANY 
and EVERY terminal you've probably delt with before. The electrical spec 
isn't similar to RS232 but current loop... it is a fundamentally different 
thing. These terminals are not only block mode, they speak a VERY robust 
protocol between the host and the display. It would be quite difficult to 
make sense out of the datastream between the terminal and host in a 
character based environment.

Again, while I don't know for sure... I would bet some cash that the M3134 
probably provided an electronic connection for the terminals, you probably 
had to do a world of programming on your own to actually talk to those 
units. And you probably had to develop your own protocol for dealing with 
fields/pages being sent back and forth. Perhaps DEC supplied a toolkit for 
doing so. But in any case, I suspect that even with their tools, you would 
NOT get a RSTS logon prompt on one just by using this card and writing a 
little code. You probably would get a toolkit that you could use to send and 
receive a page at a time to the terminal... basically you'd probably get an 
I/O device under program control.


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