An Door phone Intercom System otherwise known as intercommunication device. Some of the intercom systems integrate control of devices such as signal lights and door latches. You can see many intercoms are generally installed in buildings and vehicles.
How it works:
The built-in interface of the telephone devices allows you to install 4 door phones in the simplest way that will be only one twisted paired for each door phone, and to each hooked up to one single 2-terminal port will deliver you great performance. No other equipment will give you that much satisfaction in one package. So now avoid the hassle of complex fine tune adjustments to the door.
Portable & permanent systems:
Door phone Intercom System is designed to prevent feedback noise. No connection required to your existing doorbell button, you don’t need to do anything. No initiation tone controls to set up in order to avoid a disagreement with other equipment. Also no number-of-rings switch to adjust. No need to wire polarity to take care of. No separate enunciator is required. You hook up all your door phones simultaneously in parallel to one single port on a single unit Period. However, if you prefer individual door phone connections, then go to the QX-3 module to your package. It facilitated Video signals carried as well as voice. Several permanent types of Intercom systems found in vehicles such as aircraft, trains,watercraft, armored fighting vehicles etc.
Not a problem if you need to see your visitors too. You only required installing at your door a mini camera which you may connect directly to a television set. Or it would be better, if you connect an RF modulator to the camera if you need the entrance to be monitored from more than one television set. This video system runs simultaneously in parallel with your telephone intercom system and both complement each other. It is a perfect cost-effective solution.