Hi Tim,
Mike will certainly solve your problem once you reach him. He was
very helpful when I had a similar issue. The DB9 on the original B50
is the connection and mount for an open circuit board called a DDS
"Digital D...something.. Module". My B50 had two DB9 cables soldered
to the DDM, one for GPS output labeled "PDA" and one for GPS input
labeled "volklogger". Also soldered to the DDM is a wire running to a
toggle switch for Declare/Flight that mounts on your I/P. The B50 DDM
adds the vario data to the GPS data stream for Winpilot etc. The
first DDMs had screw terminals for a "Y" cable containing the two
DB9's (you can make this easily from a DB9 extension cable), but not
the flight/declare switch. If yours is like mine, let me know off line
and I'll forward the manual, pics of the DDM and wiring showing where
to solder things, etc.
~Bruce