Abstract: By providing an input/output housing which incorporates paired slider assemblies for supportingly maintaining a printed circuit board in secure electronic engagement between a central processor and external devices, with said printed circuit board being quickly and easily removable from the electronically engaged position, an input/output system for a programmable controller is achieved which is capable of being quickly and easily expanded as well as capable of rapid field assembly and field disassembly for removal or replacement of any required parts. In addition, the external equipment wiring is made to a terminal block which is mounted between the paired slider assemblies and pivotally engaged therein to provide readily accessible contact points for initial interconnection thereto, while also being pivotally movable and slidingly advanceable into the housing for continuous maintenance therein in a secure, hidden, easily accessible storage zone.