Master control is the technical hub of a broadcast operation common among most over-the-air television stations and networks. It is distinct from production control rooms in television studios where the activities such as switching from camera to camera are coordinated.
Master control is the final point before a signal is transmitted over-the-air or sent on to a cable television operator or satellite provider for broadcast. Television master control rooms include banks of video monitors, satellite receivers, videotape machines, transmission equipment, and, more recently, computer broadcast automation equipment for recording and playback of on-air programming.
Master control is generally staffed with one or two operators around-the-clock, every day to ensure continuous operation. Master control operators are responsible for monitoring the quality and accuracy of the on-air product, ensuring the transmission meets government regulations, troubleshooting equipment malfunctions, and preparing programming for future playback. Regulations include both technical ones (such as those against over-modulation and dead air), as well as content ones (such as indecency and station ID).
Many television and radio station groups have consolidated facilities and now operate multiple stations from one centralized, regional master control center. As an example of this centralized system on a large scale, NBC's "hub-spoke project" enables "hub" cities such as New York City, Los Angeles, and Miami to originate commercial breaks and programming for many of its smaller individual stations, thus reducing or eliminating some responsibilities and employees of the local master control at NBC-owned stations.
Outside of the United States, the Canadian Broadcasting Corporation manages four radio networks, two broadcast television networks, and several more cable/satellite radio and television services out of just two master control points (English-language services at the Canadian Broadcasting Centre and French at Maison Radio-Canada). Many other national broadcasters have taken a similar approach (although the CBC's operation is arguably more complicated than most, with local breakaways on radio and local advertisements on television).