It used to be that to install an intercom system you had to run wires and all stations were mounted on the wall. These days intercom radios enable you to put stations anywhere you want without having to run wires. The best part of that is that you can be mobile and still take intercom calls.
You can get hand-held two-way radios that communicate with table-top base station intercoms at ranges of several miles under ideal conditions. Intercom radios that use the MURS frequencies do not require an FCC license yet they communicate over long distances. You can even get outdoor wireless radio call boxes and wireless public address units that can communicate with your radio intercom system.
There are two major formats for most intercom radio systems. They are Ultra High Frequency (UHF) radio and Very High Frequency (VHF) radio. Neither frequency band is inherently better than the other. They each have their pluses and minuses. Both formats are effective ways to communicate with another person so deciding on the right radio for you depends on your application. The unlicensed MURS frequencies are in the VHF band. See this article for more info: 2-Way Radio Range
Intercom radio systems can be found at www.IntercomsOnline.com