Hollow prison gate internal air pressure monitoring procedure records pressure time characteristic during cyclic variation and compares with set reference times

摘要

A hollow prison gate (1) internal air pressure monitoring procedure uses a sensor (4) to record the pressure (P) time characteristic as it is cyclically varied to a threshold at which the pump (2) is switched off and sounds an alarm if it varies excessively from a set value. Independent claims are included for monitoring systems using the procedure.