An electronic buzzer has a tuned oscillating striker and an electronic oscillator circuit matched to the striker tuned frequency and driving the striker by close coupling of a driving coil to a core member which forms part of an electromagnetic circuit with the striker. The oscillator circuit also includes a control coil in the transistor base circuit and mounted within the driving coil for close coupling to the driving coil and the electromagnetic circuit. The control coil is optimized to have the maximum number of turns while still matching the effective input impedance of the transistor. A diode may be connected in shunt with the driving coil for improved feedback coupling and frequency tuning.

A miniature buzzer for a pocket pager and the like is provided. The buzzer includes a support member in the form of a cylindrical collar having a bore extending therethrough. The bore is stepped with the step defining a knife edge. A pole piece surrounded by a coil and ring magnet extends toward the step. The ring magnet and a central portion of the pole piece define a plane spaced apart from the step. A diaphragm, backed by a magnetic armature seats on the knife edge for attraction/repulsion toward/from the pole piece. The coil is driven by an oscillator extends from the collar. The assembly is contained within a housing the volume of which is also tuned to the oscillator.

A method for setting the air gap in an automotive horn having an armature and a stud comprises the steps of positioning the stud through an orifice so that it contacts the armature, backing the stud away from the armature a predetermined distance, and fixing the stud to the horn housing so as to establish the air gap between the armature and the stud.

A timed buzzer assembly having a rectangular base with four terminals insert molded in the base and a generally cup-shaped cover member over the base providing the housing. All of the terminals project through the base member with the armature of the buzzer supported on one terminal and the coil assembly of the buzzer supported on a second terminal. For the purpose of timing the buzzer and also controlling a warning light, a bimetal timer is provided having bimetal elements one supported on a third terminal and the other supported on the above referred to second terminal. The fourth terminal is a ground to which a heating element for the bimetal timer is connected.

An electroacoustic transducer which includes a vibratile diaphragm operating at resonance has its narrow band width response characteristic increased by an order of magnitude by the use of a uniquely designed acoustic coupler in combination with the resonant diaphragm. The acoustic resistane presented to the resonant diaphragm by the acoustic coupler dominates the motional impedance characteristic of the transducer in the resonant frequency region of the vibratile diaphragm. The use of the inventive acoustic coupler reduces the Q of the vibrating system from a value in the order of 30 or more to the order of 8 or less.