Connect a microcontroller to a gadget
For the switch at the top you can use a relay, or something like an OptoMOS.

For the buzzer detection an optoisolator with gate output with anode to buzzer +V and cathode to ground via whatever resistor is necessary to set the current specified in the datasheet - 15mA in the one linked to with a Vf of 1.4V. so if your high voltage is ~2V then 2 - 1.6 / 0.015 = 40 ohms needed. I'm assuming the low voltage is ~0V here. 

As it's an open collector output, You can wire the output straight to your Arduino pin and set a weak pullup (or just use the pin normally and use a 10k pullup to +V.