Odd Q-Bus questions 18/22bit - test-drb@ccmp.vtda.org

16 Aug 1998

...
 That paddleboard connector on the VT100 is one of the
cleverest pieces of 
design I've seen from DEC. The pins are supposed to short between the 2 
sides when there's nothing in the connector, thus linking the terminal 
logic signals to the DB25 on the back. Insert a paddleboard, and you 
disconnect them, allowing the paddleboard to connect separately to the 
VT100 logic and the outside world. 
It is neat... I used that info to create my own sort of paddleboard
attachment which allowed me to have the terminal EIA/20ma
switch-selectable... I mounted a DPDT switch in the plastic panel which
goes on the back of a VT100 20ma option and wired it so it either routed
the signals through to the EIA port or shunted them off to the 20ma
option...  only needed to intercept 4 signal lines, if I remember
correctly.. (or was it three).

I still have the 'option' in a drawer at work...

					Megan Gentry
					Former RT-11 Developer

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