Open frame electronic chassis for enclosed modules

A passively cooled modular electronic system comprising:

• an open frame chassis;
• a plurality of enclosed modules, each module enclosing electrical components;
• a plurality of chassis electrical connections on the open frame chassis for removably electrically connecting the plurality of modules to the open frame chassis;
• a support for holding each module at the inserted position where each module is in electrical contact with one of the plurality of electrical connections;
• wherein the plurality of modules are selected from two or more types of modules, each type of module having different electrical components enclosed therein and a different module electrical connection for connecting that type of module to a corresponding type of chassis electrical connection;
• and
• wherein the open frame chassis comprises key pins associated with each type of chassis electrical connection, the key pins having an orientation on the open frame chassis unique to each type of chassis electrical connection, the key pins mating with corresponding key holes in the type of module which corresponds to that type of chassis electrical connection.