Wireless doorbell to the apartment.
Installation of a doorbell in an apartment : Wireless Doorbell To The Apartment.
Quote from Article entitled Installation of a doorbell in an apartment:
Choosing a doorbell, it is better to give preference to the device in which it is possible to adjust the volume. Another useful feature is that this button will light in the dark. It operates with the help of a small LED or luminous materials. As for the appearance of the body frame and the sound there are a lot of variants. Everything will only depend on your tastes and preferences.
The full version of the article can be found here.