Abstract: An apparatus for purifying air, in particular for ventilation and air-conditioning systems, has an air filter (11), which is inserted in an air channel (10) or in a filter wall for collecting dust. A dust agglomerator (12) with a DC voltage field is connected directly upstream of the air filter (11). In conventional filters, the efficiency is increased to such an extent that the dust throughput can be approximately halved. In addition, the initial efficiency is only insignificantly reduced during the operating time.

Abstract: An apparatus for purifying air, in particular for ventilation and air-conditioning systems, has an air filter (11), which is inserted in an air channel (10) or in a filter wall for collecting dust. A dust agglomerator (12) with a DC voltage field is connected directly upstream of the air filter (11). In conventional filters, the efficiency is increased to such an extent that the dust throughput can be approximately halved. In addition, the initial efficiency is only insignificantly reduced during the operating time.

Abstract: To permit environmentally safe incineration of a filter bag together with its holding frame, and without requiring removal of the holding frame prior to incineration, the holding frame is made of fibers or cellular pulp stock, and, in plan view, is essentially rectangular. It is formed of two folded walls which, before insertion of the folding bag, are in essentially V shape, with an outer wall (6) and an inner wall (7), the V defining a gap of between 25.degree. to 50.degree., preferably about 38.degree., between which gap the filter bag is inserted. The inner wall, at the corner, is formed with a wedge-shaped gusset (9), with folding creases (10, 11) and a crest crease (12) between the folding creases. After insertion of the filter bag, the inner wall (7) is pressed against the outer wall (6), and the gussets snapped against the inner wall, to hold the frame together.

Abstract: A reference signal generator is provided for generating the two subcarrier reference frequencies for the SECAM television system. A master oscillator generates the first subcarrier reference frequency which is coupled to a divider for obtaining the horizontal line rate. The horizontal line rate is multiplied and coupled to a mixer, where it is mixed with the first subcarrier to obtain sum and difference frequencies. A crystal filter coupled to the mixer extracts the second subcarrier, which is locked in frequency and phase relationship to the first subcarrier. The signal generator also contains provisions for synchronizing the subcarriers to an external horizontal system reference.

Abstract: A system is provided for color correction of recorded television signals. The chroma signal is decoded to baseband using a reference subcarrier which has the same timing errors as the chroma signal. The stabilized baseband signal is remodulated onto a stable subcarrier and added back to luminance. The phase modulated subcarrier used for decoding is obtained from a phase modulator fed by reference subcarrier and modulated by the recorded signal burst phase error voltage. Provisions are made for processing signals recorded in NTSC or PAL format by converting the PAL alternate line burst switching to an unswitched NTSC format.