A fusing electrode is mounted on a vertically movable carriage which is raised by a first air actuator and lowered by gravity into engagement with a commutator tang. During a fusing cycle, different pressures are applied between the fusing electrode and the tang by means of a fast-acting air actuator that has a downwardly-extending piston rod engageable with the carriage and which is controlled by a programmable pressure regulating valve. To increase the response time and the force follow through of the second air actuator, the programmable pressure regulating valve is mounted directly on top of the second air actuator with its air outlet located as close to the cylinder of the second actuator as permitted by the air fittings which connect them. Surge tanks associated with the programmable valve assist in ensuring speedy response times.