Abstract: A speaker horn is adapted for coupling to a speaker drive assembly and for dispersing incident sound energy in a 360.degree. radial pattern. The horn includes two sound-dispersing structures for making a passageway generally symmetrical about a longitudinal axis. An inserted structure restricts the movement of the incident energy in one axial direction and includes a plug which is nested in close proximity to a wall of a receiving structure at the input end of the receiving structure. The receiving structure restricts the propagation of the sound energy in the other axial direction to cooperate with the inserted structure in defining the passageway in a radial pattern between the two structures. The plug includes a concave face perpendicular to the longitudinal axis for receiving incident energy. The plug, in cooperation with the inner walls of the receiving structure, effects a change in phase of sound energy encountering the plug, and acts as an intensity amplifier for incident sound energy.

Abstract: A combination changing system and method for controlling access to a locked area and updating a lock combination or memory includes encoded key cards and storing lock code combinations in a memory. Each lock may be opened by a properly encoded key card. The lock code combination is automatically changed each time a new key card is generated and used. Specifically, first and second fields of a stored code combination are stored in an active memory of the lock and first and second fields of a key code combination to be compared therewith are encoded on a key card. When the key card is inserted into a card reader connected to the lock, two fields of the stored code combination are first compared with the two fields of the key code combination, respectively. If there is a match, an appropriate signal is generated to open the lock. If there is no match, the second field of the stored code combination and first field of the key code combination are compared.