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DTMF, Dual Tone Multi Frequency, MT8870DE DTMF Decoder
Solved Ashley receives a cellphone for her birthday. The | Chegg.com
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What is a Dial Tone? (with pictures)
Tone of Voice in Communicating with a Customer | Overview, Importance & Examples - Video & Lesson Transcript | Study.com
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Everything you need to know about POTS (Plain Ordinary Telephone Service) and Analogue Phone Systems - Master 101 class | Home
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Comparing dial-tone signals - EDN
