A flameproof motor-starting contactor for use with coal-face machinery. The essential features are a flameproof casing divided into two separate compartments, the smaller of which contains a hand-operated isolating switch and the main bus bars. The isolating switch is interlocked with the cover of the main compartment so that it cannot be removed unless the switch is in the off position; or it may be fitted with contacts enabling the mechanism to be earthed before work is undertaken on it.