I needed a simple physical system to interact with a PC. In particular, a system as simple as possible (you can use with a simple gesture and no specific knowledge), effective (it should just work :)), and sure enough in order to activate the security cameras.

Along with the software part, this circuit is connected to a usb stick OneWire "DS9490R" from which it receives commands, enabling a two-color LED and a buzzer through the one-wire switch, and checking the door state. Finally present a pair of contacts "open" for the sensor iButton (the simple gesture).

Looking the board: I'm using a single dual color led, such representation is its internal schema.

"S1" is a Reed on the door, to sense if it is open. Such probe comes with 4 wires: 2 are the reed, the others are anti-tampering normal closed wire.

"J2" is a buzzer

"IC1" "IC2" "IC3" are Dallas DS2413 "1-Wire Dual Channel Addressable Switch"

"J1" are directly and straight connected to Dallas DS9490R 1-Wire USB adapter

In photo you cannot see led, iButton probe and door probe, because them are connected with the pins you can see on the right of the board...