Circuit board keying arrangement

摘要

An arrangement for keying plug-in circuit boards and their receptacles so that a user is alerted visually and audibly if an attempt is made to insert a board into an improper receptacle. Contacts on the board are arranged in coded locations along the edges of the board which slide into the guide rails of the receptacles. Contact assemblies are mounted on the guide rails in a similar coded arrangement. The contacts and contact assemblies are positioned in such a manner that at least one board contact will electrically engage a receptacle contact assembly and energize an alarm before the board can be fully inserted into an improper receptacle.