Selectively installable and removable auxiliary wiring device for I/O module

A modular I/O device includes a terminal base with a terminal block that includes a plurality of wiring connectors. An auxiliary wiring device includes a plurality of auxiliary wiring connectors and is selectively physically connectable to the terminal base in an operative position and selectively physically removable from the terminal base. The terminal block includes a receiver and the auxiliary wiring device includes a body including at least one mounting tab that projects outwardly from the body and that is located in the receiver. The receiver includes a projecting lip about which the auxiliary wiring device is pivotable relative to the receiver on a pivot axis. The terminal base includes at least one catch and the auxiliary wiring device further includes at least one latch arm that is adapted to engage the catch when the auxiliary wiring device is physically connected to said terminal base in its operative position.