Michael said it all.

The mono cable you want to save is a 15pin db wide with one bnc called dec
BC23K-03 rev 81

or do it yourself:

pin 3 gd
pin 9 +

that gives you mono output from the vs3100 motherboard. so you can use a
kbd on the 3100 and most important:  alt-f1 to alt-f9 the various consoles!
handy on slow machines

fred