For some time now I have been accusing my wife of pressing buttons on the phone in the middle of our conversations. At least once in every phone our conversation is interrupted by the distinctive tone of a button press. I'm not the only one to notice this either, as other folks she speaks with regularly also remark on how, occasionally, they hear a button press mid-call. My wife is certain that she isn't pressing anything, and is perplexed as to how this is happening. In investigating a solution to a different problem, I think I might have found the answer.
Dual-tone multi-frequency (DTMF) signaling is the technology that allows us to navigate those infuriating customer support menus. Also known as touch-tone dialing, DTMF employs the use of multiple frequencies to create a dual tone sound in the normal voice band (we can hear it) over an analog phone line. The receiver on the other end of the call can listen for these specific frequency combinations to know that a button has been pressed and react to that action in some manner.
DTMF is great when you are using an analog phone line, but VoIP and cell phones use digital signals. In order to be compatible with plain old telephone service (POTS) phones, digital phone systems will use a variety of techniques for recognizing button presses. Unfortunately, some of those techniques can be fooled by a female voice. I think this is what is happening on our phone conversations. It looks like I need to go make an apology.
We do not have a landline phone. Instead, we both carry cell phones (Verizon) and use them for all of our calling. In addition, I use Google Voice for making and receiving calls. So now the question is: which product in the chain of communication is introducing these false DTMF tones?
Have you noticed this with anyone you speak to frequently? If so, what is the chain of communication that is resulting in the errant tone? Ours is:
LG Flip Phone <-> Verizon <-> Google Voice <-> Verizon <-> Motorola DROID