DL11 configuration for pdp11gui

[Paul Koning]

> On Jun 27, 2016, at 4:14 AM, Fritz Mueller <fritzm at fritzm.org> wrote:
> 
> Okay, so I scoped the serial line, and the EIA line drivers seemed to be acting funny, mark voltage was way to high, etc....
> Somehow the VT52 could still make sense out of the wacky transmit voltages, but my MacBook certainly could not.  

How high was "too high"?  The RS232 standard rules for allowed output voltages are surprisingly lenient (3 to 15 volts, positive or negative for space and mark respectively).  But it wouldn't surprise me if modern "RS232" implementations didn't follow the spec accurately and get confused by the high end of the valid range.

	paul