Abstract: A thin, compact, high power speaker for producing high volume sound alarm signals and for reproducing voice messages, and which may be installed in a limited space. The speaker of the invention includes a housing, a transducer mounted in the housing for generating sound signals, a high pressure chamber acoustically coupled to the transducer for receiving and compressing the sound signals from the transducer, a nozzle acoustically coupled to the high pressure chamber, a sound resonance/reflection passage acoustically coupled to the nozzle to amplify and reflect the sound signals, and a sound induction passage acoustically coupled to the resonance/reflection passage to direct the amplified and reflected sound signals through the front of the speaker into the surrounding space.

Abstract: An adapter for mounting a cylindrical shell containing a magnetic reed switch and an elongated permanent magnet in respective holes in a metal door and metal door frame. The purpose of the adapter is to enable the same reed switch and actuating magnet to be used for installation on a wooden door in which the elements are held in holes in the wooden door and wooden door frame in a press fit relationship, or in a metal door in which the elements are held in the metal door and metal door frame in a self-locking relationship, thereby precluding any need for producing different reed switches and actuating magnets for wooden and metal doors. The adapter has a particular configuration to fit around the cylindrical shell of the reed switch or the elongated permanent magnet, to hold the elements locked in place in the adapter, and the adapter itself is equipped with teeth, so that when it is inserted into the hole in the door or in the frame, the teeth engage and interlock with the door or frame.