Abstract: An alarm electronic wristwatch has an electromagnetic acoustic transducer having a base plate having a plurality of upstanding projections, and a lead substrate superposed on the base plate and having a plurality of openings dimensioned to receive respective ones of the projections. The cooperation between the projections and openings enable precise positioning of the lead substrate on the base plate. The lead substrate has a set of cut-out or recessed portions in which are mounted permanent magnets. A magnetic core and excitation coil are mounted on the base plate and the terminals of the excitation coil are connected to an electrode pattern formed on the upper surface of the lead substrate. The lead substrate extends laterally of the transducer to enable electrical connection to a circuit block of the wristwatch from which drive signals may be applied to the excitation coil.

Abstract: An electronic identification and recognition system in which the recognition portion includes a voltage controlled oscillator which sweeps over a range of frequencies. The identification portion resonates at certain frequencies determined by a variable reactance in the resonant circuit in the identifier which is responsive to bits from a sequential data register. The bits result in the on-and-off switching of the variable reactance which modifies the resonant frequency in the identification portion or modifies the frequency of an oscillator in the identification portion. The changes and sequence of changes in the resonant frequency are detected and recorded by the recognition portion such that the internal code of the identifier is determined.

Abstract: A method of harmonizing the impedances of an audio amplifier and a loudspeaker interconnected therewith, the audio amplifier including a line amplifier and a positive feedback circuit for compensating for the counter electromotive force of the loudspeaker. A voice coil of the loudspeaker is mechanically driven for generating an electric signal at input terminals of the loudspeaker. Then, the amplification degree of the line amplifier or the positive feedback circuit is adjusted to reduce the signal voltage between the input terminals of the loudespeaker to a minimum, during the circulation of the generated signal through the positive feedback circuit and the line amplifier.