[Coco] 8-Bit Microcomputers

[David Hazelton]

KnudsenMJ at aol.com wrote:

> industry-standard floppy interface was a real gift, and we didn't waste it!
> 
> Also, despite the jokes about Tandy's serial printers and modems, that 
> interface was standard RS-232, once you got past the 4-pin DIN connector (which hung 
> from the walls in Rad Shack store).  And the manual documented the pinouts.
> 

Actually, it wasn't standard RS-232, Since if I remember right it was 
+3/-3v instead of +5/-5v.  This actually helped me at a job I once had. 
  I worked at Cabletron and I had a sales person call me to ask why 
Cabletron's Terminal Server (Xylogic's Annex3 in a Cabletron hub) 
couldn't see a RS-232 device.  A Unix machine was polling the ports to 
read power gauges.  While Cabletron's Terminal Server sat there blankly 
along with 2 other companies Terminal Servers, Cisco's Terminal Server 
was reading the gauges happily.  It made Cabletron look bad.  Well, 
Cabletron at the time resold Cisco routers redesigned for thier hub, so 
I called up a Cisco engineer to ask him, he didn't know off the top of 
his head, but when I mentioned that it acted like the guage voltage 
wasn't high enough and that I had seen a system that RS-232 was based as 
+3/-3v, he looked at the schematics.  True enough that was the problem, 
testing the gauges voltage, it never went above 3.5 volts.  Cabletron 
lost the contract and Cisco won.


~David Hazelton