Importance

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Abstract

This circuit, controlled by the counter (Z) and via the row transistors (ZTm) and upon actuation of a pushbutton key, successively interrogates the row lines (1m) and, via the column line (2n) as connected to the row line, forms an inverter with the corresponding resistor (SRn), so that an L level will appear at the input of the corresponding column inverter (SI1n). In the ROM-type matrix (M), with the aid of the matrix transistors (T . . . ) and the resistors (MRmn) it is accomplished that the m.multidot.n lines (Lmn) are only controlled in such a way that the corresponding line conducts an H level upon actuating only one single pushbutton key of the keyboard (TF). Accordingly, a l-ex-m-times-n code appears on the lines (Lmn) which, via the NOR gate (N) also effects the release of the counter (Z) counting the clock pulses of the clock pulse generator (TG).

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First Claim