A very simple logic tester that has a seven-segment display to indicate High or Low, and a small speaker that emits a sound scheme properly can be done using electronic below.
If the input signal is "0" logic, the display shows L and the speaker emits a low note. When the input signal is "1" logic, H appears on the display and the speaker emits a tone that is one octave higher than low grade .
When the input signal is "1" drive transistor T1, N2 gate leading into the tipping threshold and trigger output goes to logical "0". Transistor T2 (pnp) is locked: entry gate N1 is also above the tipping and the trigger output is therefore all "0" logic. I-Belle comutatieT3 and T4 transistors are blocked and the current through the corresponding segments (bc e, f. g) diodes D4 and D5 and R7.
When the input signal is "0" logic leads T1 and T2 is blocked. The input voltage gates N1 and N2 are both below the tipping and outputs are "1" logic, unlocking the transistors T3 and T4, T4's emitter voltage grow and block diodes D4 and D5, causing a current through the segments d, e and f, diodes D2 and D3, resistance R6 and transistor T3.