Abstract: A three-phase-encapsulated high-voltage circuit breaker, arranged horizontally and with a compact construction, is intended to have as small a physical height as possible and to require as small an installation area as possible. To this end, the tubular switch enclosure is provided at each of its ends with a connecting flange for horizontal connection of a surface-mounted enclosure. The drive device is attached to a mounting flange in the casing region of the switch enclosure. The circuit breaker poles are supported via insulating posts on the casing of the switch enclosure and are in the form of bushings for the coupling elements which are connected to the drive device. The power movement of a lever drive arranged downstream of a coupling element passes via a direction-changing lever which is mounted in the respective circuit breaker pole. The internal construction of such a circuit breaker may also be applied to single-phase-encapsulated circuit breakers.