A modular-construction control casing is proposed for the integration of plug-in connectors and additional electronic equipment within an electronic casing which is located, in a decentralized manner, close to the consumer's installation. The casing, having the form of a rectangular parallelepiped, is formed from two identical half-shells, at least one mounting plate or printed-circuit board being mountable within the casing. Provided at the narrow sides of the casing are openings which can receive either a plate part for the closure of the casing and/or for the mounting of control elements, or into which there can be inserted, with a form-fit, an adapter which is provided for receiving already known plug-in connectors.