Conference calls are phone calls that involve three or more people at the same time. A phone bridge facilitates a conference call with a certain number of people who enter a code that allows them to listen to what is being said but does not give them the opportunity to speak to the group.
A phone bridge is useful when you need to get information to a large number of people and do not need to receive feedback from them. Classes on specific topics and employee training are two examples of when this might be appropriate.
According to Telephone Bridge Services, companies charge an hourly fee for phone bridges, depending on the number of lines involved. The hourly rate typically is about $1 for every line you wish to have.
A phone bridge can either be call-in or call-out. A call-in bridge requires that the people who wish to access the audio call a number given to them. With a call-out bridge, the person conducting the audio calls each participant.