This is a drawing of the DB50 connector that I will be using to connect my control panel to my layout.
This is the layout end of a 50 pin female connector. Pin 1 is paired with pin 26, pin 2 is paired with pin 27 and etc for 25 pairs or blocks. The connector is 2" long by just under a ½" wide. The connectors are available at Fry's. I use a DB37, 37 pin connector for my turnout controls. I standardized on the DB series connectors for their compact size. I also use DB25 connectors for lighting and DB 15s for signals. By reversing the male and female connectors I can use two pairs of each type without the possibility of accidentally reversing the connectors.