One late night many decades ago, I chanced upon a technical description of the Touch-Tone system. The book I was reading had an explanation of how each key on a telephone sends a combination of two ...

When was the last time you heard a dial tone? If you’re young enough, you might not even know what a dial tone is. You might not understand that we used to hear a droning buzz whenever we picked up ...

All products featured here are independently selected by our editors and writers. If you buy something through links on our site, Gizmodo may earn an affiliate commission. Reading time 2 minutes In ...

• 9.0 PSTN operator Most organizations have, and continue to use, a 9 to access an outside line. When a 9 is dialed, a secondary dial tone (stutter tone) is heard. Some legacy PBX (private branch ...