An electric drill has a drive assembly, and a pivot head having first and second bit gripping assemblies disposed at 90 degrees to each other. Elongated horizontal slots are located in sides of the receptor for receiving locking pins also inserted through holes in the vertical posts. The fault-detecting circuit is configured to select one of the outputs of the second shift register and a first serial input signal based on the fault-detecting result. The data is encrypted using the respective key to form the encrypted data.