Abstract: An improved security system comprising a relay selectably operable to pass electrical power to a protected device, a code plug having a preset combination of possible electrical connections controlling passage of electrical current to actuate said relay, a key carried by an authorized person insertable into said code plug to complete preset combination of connections, and a switch box connected in series between said code plug and said relay having a plurality of multiposition switches each having a plurality of contacts selectably connectable by a person seeking to limit access to said protected device in a manner to define a desired combination to which said switches must be set in order to allow said switch box to pass said current to said relay.