Abstract: An air purifying apparatus that has an ozone generator which generates plasma field in the ultraviolet region. It utilizes a pair of electrodes in the form of plates that are separated by an insulator. The plates are connected to a high-voltage transformer through diodes in such a way that only a negative and less positive charges appear on the plates. The generator is provided with a self-cleaning apparatus in which the circulating air fan that is provided for normally forcing air through the electrostatic plates may be turned off for a period of time and the ozone generated by the plates at that point in time will tend to combine with the contaminates and oxidize the same.

Abstract: A lightweight piezoelectric microphone using a metallized piezoelectric diaphragm arcuately bowed by a boss on a slotted baffle plate held in close parallel proximity to the diaphragm is disclosed. Slotted Helmholtz resonators provide frequency response shaping and wide band noise cancellation. Electrical contact between the diaphragm and an electrical conductor is provided by a conductive, elastic material compressed by parts of the microphone housing, into electrical contact with the conductor and a metallized side of the diaphragm.