The OP5980-2 DB37 Breakout Diagnostic Module enables users to isolate individual pins originating from a DB37 connector, and to test for connections.
Each of the 37 pins leads to a labeled and exposed site on the visible portion of the card attached to the connector: the metallic side of the site is for live connections, while the light/LED side is to establish whether connection has been made.
A DB37 connector has 37 pins arranged in two rows, with one row on top of the other. The top row has 19 pins and the lower row has 18. This connector is used sometimes with networking hardware, and other applications using RS-449 serial communication.