(57) Electronic locking system including keys (30) and self-sufficient door locking units
(50) both of which carry multiple "zone" codes (F1,F2...). Upon recognition of a key
(30) by a door unit (50), the zone codes within the key and door unit are matched
against each other so that a match between any one of the key zone codes (FI) and
any one of the door unit zone codes (FJ) will result in an "allow access" decision
(366). In the "basic zone" function (350), this decision will permit unlocking of
the door (368); in other keying system functions or features (330), additional steps
may be required for such unlocking, and the coding of either the key or door unit
may be altered (340). The keying system architecture, and method of issuing keys,
may be defined in terms of a directed acyclic "door group" graph (400) or equivalent
data structure, door groups (401,402...) being defined hierarchically as door units,
groups of door units, or groups of door groups. Each node of this graph (400) is identified
with a given door group and, except for terminal modes (404,405,415,417,422-429) (which
are typically identified with given door units), each such node has an associated
"choice rule" (450). In issuing keys (30) the key issuing operator, working from a
given door group (401) as the starting point, traverses subordinate nodes (402,403...)
subject to limitations and decisions imposed by the choice rules (450), until only
terminal nodes (404,405....) remain -- thereby defining the coding of a particular
key.
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