Abstract: An apparatus for ionizing air to remove particulate matter. The apparatus including an ionizer and a bracket for mounting the ionizer and a bracket for mounting the ionizer in a duct or enclosure. The ionizer includes a series of electrodes which span a portion of the duct. The electrodes are energized by a high voltage circuit and an ionic wind is created between the electrode and duct. The ionic wind sweeps particles in the air to the duct which provides a collector electrode. In another embodiment, a ring collector electrode is also provided for spanning the inner portion of the duct. The high voltage circuit includes a DC power supply, a high voltage transformer, a high voltage multiplier stage and a push-pull switching circuit. The DC power supply receives AC power and generates a DC output which is coupled to the primary of the transformer. The push-pull switching circuit produces a controlled and efficient AC output in the transformer by alternately switching the primary winding.

Abstract: An apparatus for ionizing air to remove particulate matter. The apparatus including an ionizer and a bracket for mounting the ionizer in a duct or enclosure. The ionizer includes a series of electrodes which span a portion of the duct. The electrodes are energized by a high voltage circuit and an ionic wind is created between the electrode and duct. The ionic wind sweeps particles in the air to the duct which provides a collector electrode. In another embodiment, a ring collector electrode is also provided for spanning the inner portion of the duct. The high voltage circuit includes a DC power supply, a high voltage transformer, a high voltage multiplier stage and a push-pull switching circuit. The DC power supply receives AC power and generates a DC output which is coupled to the primary of the transformer. The push-pull switching circuit produces a controlled and efficient AC output in the transformer by alternately switching the primary winding.

Abstract: A masking sound source for a sound masking system has adjustable preset means for adjusting the spectral shape of the sound produced. The source includes a random noise generator for producing white noise and having two incoherent outputs in which two low pass filters having different frequency response characteristics are connected. The filtered noise signals are applied to a potential divider forming a contour control device by which a composite noise signal having the requisite spectral shape is derived. This composite noise signal, after appropriate level adjustment, is applied to an output amplifier.