Abstract: A glass composition for a photoetching mask is described, which comprises, all by mol, 55 to 70% SiO.sub.2, 7 to 11% Al.sub.2 O.sub.3, 7 to 20% CaO, 3 to 13% MgO, 3 to 13% ZnO, 0.5 to 3% K.sub.2 O or Na.sub.2 O, 0 to 11% PbO and 0 to 3% ZrO.sub.2. This glass is free from defects such as pinholes, has a relatively low coefficient of thermal expansion and contains no air bubbles, and a photoetching mask composed of the glass composition.

Abstract: An alkali-free glass composition for a photoetching mask is described, which comprises, all by mol, 55 to 65% SiO.sub.2, 7 to 11% Al.sub.2 O.sub.3, 1 to 11% PbO, 7 to 20% CaO, 3 to 13% MgO, 3 to 13% ZnO, 0 to 3% ZrO.sub.2, 0 to 3% F.sub.2, 0 to 5% As.sub.2 O.sub.3, and 0 to 5% Sb.sub.2 O.sub.3. This glass is free from defects such as pinholes, has a relatively low coefficient of thermal expansion and contains no air bubbles, and a photoetching mask composed of the glass composition.

Abstract: An information signal recording system comprises a circuit for generating pilot signals for tracking control, a circuit for generating a rectangular waveform signal of a specific frequency existing in an artificial synchronizing signal duration in every specific period and having almost no frequency component equal to and in the vicinity of the frequencies of the pilot signals, a circuit for pulse code modulating or difference modulating an information signal, further digital modulating the information signal, and obtaining a digital information signal existing in a time interval other than the artificial synchronizing signal duration. The digital information signal is recorded along a main track on a recording medium and the pilot signals are recorded along pilot signal tracks contiguous to the main track.

Abstract: The present system comprises (a) a character input unit for providing the coordinates of a plurality of points of an input character, (b) a pre-process unit for normalizing the size and the position of said input character, (c) three points approximate unit for providing three feature points for each stroke of the input character, (d) a reference pattern storage for providing the coordinates of the feature points for each stroke of the reference characters, (e) a stroke difference calculator for providing the sum p.sub.i of the length between the feature points of the k'th stroke of the input character and the feature points of the i'th stroke of the j'th reference character, (f) a storage for storing the stroke difference p.sub.i, (g) means for operating the members (e) and (f) repetitively for all the strokes of the j'th reference character, (h) means for detecting the minimum value p.sub.min among the stroke difference p.sub.

Abstract: In a record disc reproducing apparatus, an abnormal sound eliminating system comprises a variable filter in the transmission system for a signal reproduced from a record disc. The filter does not pass the signal band, which is variable. A control signal generator produces a control signal in accordance with the frequency of a carrier wave reproduced from a multichannel record disc. The non-passed signal band of the variable filter is variably controlled by the control signal from the control signal generator, to eliminate a carrier wave reproduced with a frequency lower than a specific frequency. This low frequency wave appears when the multichannel record disc rotates at a low speed, less than a specific normal rotational speed. This limitation prevents the generation of abnormal sound due to the reproduced carrier wave of low frequency.