[Rogal] wrote a cell phone application called ToneTool that generates audio tone sequences. It can be used to output DTMF and SelCall sequences which are used by telephone systems and ...

Sometimes you start building, and the project evolves. Layers upon layers of functionality accrue, accrete, and otherwise just pile up. Or at least we’re guessing that’s what happened with [Varun ...

Using dual-tone multi-frequency (DTMF) technology provided “touch-tone” service that would become the worldwide standard for telecommunication signaling. The system uses audible tones for each of the ...

This tutorial describes how low cost, low power CPLDs can be used to expand a typical handset DTMF keypad into a QWERTY keypad. As cell phones and other portable handheld devices continue to add ...