The cause was a faulty automatic switch.

Guidant also would not say what percentage of its defibrillator sales were affected by the faulty switch.

Investigation later found this to have been caused by a faulty micro switch.

For months, they had complained of a faulty main electrical switch, live wires on the ground and ventilation so poor that they sweated in winter.

Mr. Bermea said he did not know if the mining machine with the faulty switch was in use at the time of the explosion.

When ready to replace the faulty switch, mark the wire connected to the common terminal with a piece of tape to prevent confusion.

When such an outlet does not work because of a faulty switch, testing is required.

The problem would not have occurred had the faulty switch failed completely, Mr. Britz said.

A faulty switch caused a surge of current to the turbine, igniting insulating material on some electrical wiring.

However, it had not done so, because of the faulty switch in the auto-return module.