Housing for a multi-board electronic module for a programmable controller system

An electronic module of a programmable controller system, said electronic module including a housing to enclose a plurality of electronic circuit boards, said housing comprising:

• a rear wall, side walls, a top wall and a bottom wall cooperating to define an enclosure having an open front;
• a cap enclosing a portion of said top wall and a portion of said rear wall, said cap adapted for wall mounting of said housing;
• a removable cover closing said open front;
• an electronic circuit board mounting means located in said housing for mounting said electronic circuit boards in a substantially vertical orientation;
• vent openings in said top and said bottom walls,
• said vent openings and said vertically oriented electronic circuit boards cooperating to permit air heated by components on said electronic circuit boards to escape said housing through said top wall vent openings and for permitting ambient air to enter said bottom wall vent openings, thereby replacing said escaping air and cooling said components on said electronic circuit boards.