Census® and Cyphertag® have been used extensively in UK prisons and secure mental hospitals to avoid key compromises from occurring. Robust uniquely coded key-fob tags are securely attached to the keysets. All exit portals from the establishments are covered with a form of loop aerial reader. The readers detect the presence of a site tag and raise an alarm locally. The readers are, in some installations, connected to a site management system to record the identity of the individual tag and the time and date when the potential compromise occurred. Hand held readers are often supplied to enable random checks to be undertaken through the establishment.