high and low tester

100 high and low tester R. Storn This is not our first high and low tester, but the present circuit offers something new: a seven-segment display which shows "H" or "L" and at the same time a small loudspeaker emits a corresponding tone. And all th at at very reasonable cost. When the supply is switched on, the decimal point of the display lights and indicates that the unit is ready for use. If this is not the case, or an undefined signal is applied to the input, the display, apart from the decimal point, remains dark and the loudspeaker remains silent. It the input signal is logic 0, the display shows "L" and the loudspeaker emits a low note. When the input signal is logic 1, the display shows "H" and the loudspeaker emits a note which is an octave higher than the low" tone. Operation of the circuit can be seen from the circuit diagram in figure 1 and the truth table in figure 2. When the input signal is 1, transistor T1 conducts taking the input of gate N2 above the trigger thre...