Simple Touch Tone Generator

The oscillator is a Motorola MC14410CP chip using a 1-Mhz crystal. The chip generates both the high and low tones, feeding the energy to the amplifier through 1-K resistors and the 1-uF capacitor. Values for the output resistors can vary from a few hundred ohms to about 60 K ohms. The value of the resistor shunting the crystal can vary from about 3 to 15 Mohms. The amplifier consists of an LM-380N.

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Simple Touch Tone Generator - Circuitos de Electronica