A device that combines the data streams from many simultaneously active inputs into one shared channel in such a way that the streams can be separated after transmission. The concentrator's output bandwidth must be at least as great as the total bandwidth of all simultaneously active inputs. A concentrator is one kind of multiplexing device.

For example, a concentrator may be used to connect 24 2400 bps TTYs to a host via a 57600 bps channel.