I'm just trying to solve a problem. I'm a motorcycle rider and the hassle of pulling over, taking off my gloves, getting my phone out of my pocket, etc, every time it rings drives me nuts. I can use an off the shelf headset and throat mic, but it is nearly impossible for me to hit an inline call answer button with gloved fingers. So r bat leads me to the project:
I want to build a big call answer button that I could plug inline with 3.5mm jacks. I dont understand the electronics involved in telling the phone to answer and hang up. Any help would be appreciated.

 

most phones have an auto-answer feature, that just connects the call when someone is ringing in. If that's what you want or not I don't know.

You could also just buy a headset with an answer button, then modify it to make it fit your needs.

 

Zing! You just solved my problem! I never knew about that setting! I'm still interested in the project just for fun. What tells the phone to answer the call? It has to be universal and the buttons are tiny. Is it just energizing the circuit?