Abstract: An electret film is formed on the rear side of a front face plate of a cylindrical capsule made of aluminum . Closely in spaced opposition thereto, an electrically conductive diaphragm is held by an electrically conductive holding member. A wiring board provided behind the holding member closes the rear end of the capsule. The rear end of the capsule is bent on the rear periphery of the wiring board, and calked thereat. In the capsule, an impedance conversion IC device is connected to the electrically conductive holding member and the wiring board.

Abstract: For regulating the vibration frequency of a tuning-fork vibrator to a desired frequency, the tuning-fork vibrator is regulated so that its vibration frequency may become a frequency lower than the desired frequency by a predetermined value, and then the tuning-fork vibrator is regulated so that a difference between proper vibration frequencies of both legs of the vibrator may become smaller than a predetermined value, and further, the vibrator is regulated so that the desired frequency may be reached, while maintaining the difference in the proper vibration frequency smaller than the predetermined value. In this way, the desired frequency can rapidly be attained.

Abstract: First and second color liquid crystal display elements of the negative guest-host type are disposed in adjacent and opposing relation to each other and the color liquid crystal display elements provide display in different colors, at least one of electrodes of each color liquid crystal display element having formed therein a display pattern. By the control of a changeover switch, an alternating drive voltage is applied from a drive circuit to one of the first and second color liquid crystal display elements to change the color of a background of the display in accordance with the control of the changeover switch.

Abstract: A rear view mirror for a two-wheeled vehicle with a radio receiver set contained in the mirror case housing.