There are basically three types of intercoms available (click on the links below for detailed information):
If there are no wires in place currently and you don't want the
expense or hassle of running them, then a wireless intercom system may
be a good choice. Wireless systems are very quick to install and in most
cases provide similar capabilities to a wired system.
How to Choose the Perfect Wireless Intercom
If you have a building under construction, wires already in place, or
you don't mind running wires, then a wired system may be for you. Wired
systems are often less expensive and in some environments where wireless
signals may not reach, they may be the only option.
How to Choose the Perfect Wired Intercom
For applications where you need to both see and talk to a visitor at
a door or entryway, then you need a video intercom. Most video intercoms
are wired systems since video is much more difficult to send wirelessly
than audio only systems.
How to Choose the Perfect Video Intercom