Here is a picture of the Systems 9000 control head connector and the DEK connector:
http://www.open.org/~blenderm/syntorx/c ... tml#dekcbl
The first 14 pin connector plugs into the Systems 9000 control head VIP connector and the second 6 pin connector plugs into the DEK. Another DEK cable with the first 14 pin connector also plugs into the 1st DEK to daisy chain to a 2nd DEK (the second 6 pin connector plugs into the 2nd DEK). Same way with a 3rd DEK.
Here is a picture of the connector that plugs into the other DEK pins not used by the first 2 connectors above:
http://www.open.org/~blenderm/syntorx/c ... l#dekvipii
When you install a DEK the VIP ports are transferred from the control head to the DEK.
If you put the pictures of all 3 cable connectors together they will show you pin assignments for the connectors that plug into the DEK which you can use to identify the DEK pins (the pin numbers also match the Systems 9000 control head pin numbers). Keep in mind that pins 6, 9, 22, 25, 39 and 42 have been removed to make room for the connector bodies. If you remove these 6 pins from a DB-50 male connector you can duplicate the control head and DEK connector that are mounted on the circuit board. You can also use the missing pins to figure out which cable connector goes where when deciphering the pin numbers.
This is the pin out for the HLN1239 and HLN1241. There are some other things out there that look like a DEK that may not use this pin out.