Protection of supply metering.

摘要

In combination with electronic circuitry (10) which controls the operator of a meter (20) which centres commodity supply, there is provided apparatus for protecting the circuitry against interfering high voltage discharges, comprising a memory (14) on which a pattern of signals is stored by a watchdog curcuit (24) when an orderly shutdown of the controller occurs, for example due to credit expiry, and when the controller is restored to power, the watchdog circuit reads the memory and generates a shutdown control signal of the stored signal pattern is not preset in the memory.