Abstract: A circuit module is disclosed wherein a supporting framework for the module also serves as a voltage and ground bus structure for providing appropriate connections for voltage distribution to circuit boards which are assembled on the framework to form the walls of the module. This facilitates the use of circuit board input-outupt connections on all edges. The completed structure forms a hollow configuration which acts as a plenum chamber to facilitate the cooling of components mounted on the circuit boards. Two different types of supporting frameworks are disclosed. Also disclosed are arrangements for disposing assemblies of circuit modules within cabinets in such a manner as to facilitate ready access thereto.