Abstract: An alert apparatus for a personal communication device includes a mechanically prestressed piezoelectric wafer positioned within the personal communication device and an alternating voltage input line coupled at two points of the wafer where polarity is recognized. The alert apparatus also includes a variable frequency device coupled to the alternating voltage input line, operative to switch the alternating voltage on the alternating voltage input line at least between an alternating voltage having a first frequency and an alternating voltage having a second frequency. The first frequency is preferably sufficiently high so as to cause the wafer to vibrate at a resulting frequency that produces a sound perceptible by a human ear, and the second frequency is preferably sufficiently low so as to cause the wafer to vibrate at a resulting frequency that produces a vibration readily felt by a holder of the personal communication device.

Abstract: A vibrating transducer or alarm for a pager, cellular telephone and the like, includes a single coil wound in a longitudinal direction to enclose a chamber extending in the longitudinal direction; a planar substrate, bonded to an outer wall formed by the coil; a switching power source, operatively coupled to the coil, for producing an oscillating magnetic field within the chamber; and an eccentric weight rotor assembly extending within the chamber, where the rotor assembly includes a permanent magnet that provides a rotational force to the rotor assembly when acted upon by the oscillating magnetic field.

Abstract: A piezoelectric buzzer has a piezoelectric crystal mounted on a circular mounting plate. Supporting struts are integrally formed in the mounting plate by punching strut shaped portions in the plate and bending these portions such that they are substantially perpendicular to the plate. The struts are positioned on the nodal circle of the transducer so that the vibration of the transducer is not substantially impaired by the mounting arrangement. An oscillator circuit is connected to provide a potential between the mounting plate and a first electrode positioned on the surface of the crystal opposite the mounting plate. A second electrode, positioned on the surface of the piezoelectric crystal adjacent the first electrode, provides a feedback signal to the oscillator circuit. The unique buzzer design allows the buzzer components to be assembled by a one-step soldering process.

Abstract: A modular buzzer device which includes a striker arm, a diaphragm, and electromagnetic means for oscillating the striker arm. The device is housed in a container with a shape and size corresponding to a common electronic component configuration. The diaphragm is molded onto the housing and forms the top wall thereof. The striker arm is welded to one leg of an iron core used in oscillating the striker arm.

Abstract: 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.