TDS-2240 is a digital speaker selector that controls 24 zones, extend to maximum 768 zones by grouping 32 pcs of TDS-2240. It supports 2 wire mode & 3 wire mode of speaker cabling. 2 color 24 LED switches allow user to select any combination up to 24 zones independently. 2 color 24 LED switch for easy identification of currently selected status. LED lights green in normal mode, red in emergency mode.