Smartphone / cellphone headset clicker V2

Improved version. See original for more details.

We can eliminate the Zener diode from the original design by setting the IC pin to high-resistance (i.e. setting it to "input" mode) when we want the NPN gated off. We can drive the NPN gate open without changing the IC pin mode by simply connecting the internal pull-up resistor. R1 is included simply to protect the phone; this is probably not necessary, but everything functions with R1 10 Ohm, which better matches what my test headset does.

Code is included. Arduino functions are not named very well for using the pin in this manner, so I renamed them.

(I tried eliminating the transistor too, by connecting the Arduino pin directly to the microphone line and then switching it between open and grounded, but that didn't seem to work. May not be a good idea to have the microcontroller in input mode and receiving negative bias; not sure.)