The Numark BCM-135 Beatkeeper II is developed in the USA by Advanced Audio Concepts. It is a plugin device that helps you synchronize multiple audio tracks. Via a visual indicator the Beat keeper informs you about the BPM and offset of the playing tracks. It doesn't do the mixing/synchronising for you, but helps you get it right.
Features
Automatic MIX tracking of up to 4 input sources simultaneously
Autosensing circuitry for 4 phono or line inputs
All visual displays update on every beat
Accurate digital BPM displays
Visual live tracking of your mix progress using Tempo Difference and Beat Offset Bar Graphs
Sync Lock Button for accurate BPM tracking
BPM Range for quicker searching
Beat Assist for locking to the correct beat
Simple user interface
19', 1 Rack Space