EDN Access -- 02.03.94 Circuit vocalizes telephone numbe

-February 03, 1994

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Design Ideas:February 3, 1994

Circuit vocalizes telephone number

Shwang-Shi Bai,
Chun-Shan Institute of Science and Technology, Lung-Tan, Taiwan

The circuit in Fig 1 is a simple method of vocalizing the digit number of a telephone keypad, which, for someone visually impaired, provides helpful voice confirmation. A 75T202 dual-tone multifrequency (DTMF) receiver decodes the DTMF signal when you depress the phone's keypad. The TC8801N voice synthesizer outputs the voice data corresponding to the data input code. A TA7368P audio power IC amplifies the result. The logic gates perform necessary code conversion for the voice-synthesizing IC's input. (DI #1357)

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