Conference bridging

A conference bridge allows a group of people to participate in a phone call.  The most common form of bridge which allows participants dial into a virtual meeting room from their own phone.  Meeting rooms can hold dozens or even hundreds of participants.  This is in contrast to three-way calling, a standard feature of most phone systems which only allows a total of three participants.  For most phone systems, conference bridging is an add-on feature that costs thousands of dollars.