Doorbells are usually placed next to the front door so that visitors can make themselves noticed with the gong. The intercom can be installed in combination with the doorbell so that you can talk to the guest before entering.
Today, wireless, smart doorbells and smart door openers are widely used, which transmit data via WLAN and can be operated from a mobile phone. These doorbells usually integrate a camera and an intercom system, which allow monitoring the entrance to the house with the video doorbell via an app on the telephone.
In addition, there are still the classic doorbells with other transmission methods such as radio or cable.