One Way, Voice Activated Intercom

An omnidirectional electret microphone can be used to pick up the sound and convert it into an electric signal. The output of the microphone is fed along two paths. In the first path, the signal is send to the inverting input at pin 6. In the second path, the microphone signal is fed to the non-inverting input of U2, where it is amplified and output to the speaker, SPKR1.

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One Way, Voice Activated Intercom - Circuitos de Electronica