Three in one Tone Generator

Various tone generator circuit is already published in Now, here is unique tone generator circuit which produces three different type of sound according to input three different logic levels (i.e. 0&1, 1&0 and 1&1).

Circuit description

This circuit is designed around digital IC 7400 which is NAND gate. The working of the circuit is like the working principle of oscillator circuit, where frequency depends upon capacitors C1 and C2. The duty cycle of this circuit is 50%. The output is given to power amplifier circuit which further drive loudspeaker or head phone. For low frequency value of capacitor C1 and C2 must be high and vice-versa.

circuit diagram of three tone generator


Resistors (all ¼-watt, ± 5% Carbon)

R1, R4 = 1.2 KΩ

R2, R3 = 1 KΩ

R5 = 10 KΩ

R6, R7 = 47 KΩ


C1 = 100 kpF

C2 = 220 kpF

C3, C4 = 10 kpF


IC1 = 7400 (NAND gate)

D1, D2 = 1N4148

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