In this chapter, we'll be using a real home AC inter-communicator with a building entrance door unlock button and this will require you to do some homework. This integration will require you to open your inter-communicator and adjust the inner circuit, so be aware that there are always risks of damaging it.

If you don't want to use a real inter-communicator, you can replace it by an LED or even by the buzzer module we used in the previous chapter. If you want to use a real device, you can use a DC inter-communicator, but in this guide, we'll only be explaining how to do the wiring using an AC inter-communicator.

The first thing you have to do is to take a look at the device manual and check whether it works with AC current, and the voltage it requires. If you can't locate your product manual, search for it online.

In this chapter, we'll be using the solid state relay we previously used in Chapter 4, Creating a Motion Sensing Light. This relay accepts a voltage range from...