The DO-5 provides 16 open collector output circuits for controlling the TEL REL 002 relay board. Power for the external relay circuits is provided by the +12VDC bus on the backplane with a maximum of three DO-5 modules per backplane/PS-xx power supply. 

The insert in the hinged cover of the terminal strip has circuit wiring information. Circuit identification information can be recorded on the outside surface of the insert. The outside left edge of the insert is color-coded red to indicate a high-voltage module.