Communications: electrical – Continuously variable indicating – With meter reading
Patent
1989-01-27
1991-01-29
Dwyer, James L.
Communications: electrical
Continuously variable indicating
With meter reading
70 63, 70271, 2353825, E05B 4900
Patent
active
049889877
ABSTRACT:
An electronic lock system is disclosed in which a key can be assigned a limited lifetime, such as by storing data indicative of an expiration date in a key memory. Whenever the key is used with a lock, the lock first examines this key data and verifies that the key is still timely before performing any operations. After a key's expiration date has passed, it is useless until a new expiration date is stored in its memory. By this arrangement, keys that are lost or stolen soon lose their efficacy and no longer pose a threat to system security. The invention also permits the lock administrator to issue keys with different useful lives, so that, for example, a person who needs a key for only one day can be issued a key that expires the next day. A variety of other operational features are also disclosed.
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Barrett Philip D.
Henderson Walter G.
Larson Wayne F.
Dwyer James L.
Supra Products, Inc.
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