Patent US 4,095,739

A security system in which access at remote locations is limited to personnel inserting in the system a coded data card, the data of which compares favorably with data stored in a memory. The memory data comprises a table which permits access to selected terminals by selected personnel at selected times. Programming access to the system for the purpose of altering data in the access authorization table is limited to individuals who insert a supervisor's card into the system, which card enables the logic required for altering the authorization table.