A satellite multiswitch is a device used with a dual or quattro LNB to distribute satellite TV signals to multiple (usually more than four) receivers from a single dish and LNB.
The Quattro LNB provides the signals for all four of the modes at the same time. The satellite multiswitch then selects which of these signals to send to each receiver. For very large installations the signals from the LNB can be split and fed to more than one satellite multiswitch. Typically a larger dish is used to make up for the extra losses in the longer cable runs and the satellite multiswitches.
Some satellite multiswitches can also mix in terrestrial TV and FM radio signals which can then be split out again by a special faceplate (known as a triplexer). Such Integrated Reception Systems allows satellite, TV, and radio service to be supplied down a single cable saving on installation costs.
Satellite multiswitches are commonly installed on or in blocks of flats to allow all the residents to receive satellite TV without having to have a separate dish for every resident.