Alarms; Coaxial cables; Electric door bells; Electric plugs; Electronic access control systems for interlocking doors; Locks, electric; Megaphones; Monitors (computer hardware); Peepholes (magnifying lenses) for doors; Punched card machines for offices; Push buttons for bells; Switchboards; Tape recorders; Telephone receivers; Video baby monitors; Video projectors; Video recorders; Video screens; Video telephones; Telephone transmitters