The 555 acts as the tone
generator configured in the astable mode. Its pin 3, square-wave output is transformed
into a triangle wave by R1 and C2. The voice's pitch is controlled by R1. Transistor Q1
can be 2N1086, 2N1091, or any other equivalent npn germanium type. Sounds are amplified by
the 741, and the ICS's output drives the transistor to saturation. When the transistor is
in the saturated state, the triangle wave is able to reach the speaker, and your new voice
can be heard. |