Abstract: A single pull rod mechanism for actuating the contacts of each phase of a three-phase gas insulated circuit breaker arrangement utilizes acceleration springs only in relation to the second and third phases. Contact parting velocity is measured externally of the breaker thereby providing a check on the breaker operation without breaking the integrity of the gas tight tanks. An eight valve gas system utilizing an integral manifold provides for a complete circulatory arrangement for the high and low pressure gas for all three phases of the circuit breakers increasing the operating reliability of the circuit breaker while simplifying routine and major maintenance procedures.