Modern Video Door Phone
Installation of a doorbell in an apartment : Modern Video Door Phone
Quote from Article entitled Installation of a doorbell in an apartment:
Electric bell operation is impossible without electricity. Therefore, to the place where a device will be fixed the must be wired. As a general rule, wire products work on AC power with the voltage of 220V. You can use a single two-wire cable or two single-wire cables. Wire section may be of 0.5 square millimeter or more. However, it is not necessary to use thicker wire because the power consumed by wired bell is little. The only thing to consider is its material. It should be the same as for wiring throughout a house or an apartment.
The full version of the article can be found here.