The Edwards 5531M Adaptatone Millennium is a heavy-duty industrial, tone-selectable, signaling device capable of producing volume-controlled, high-decibel tones, four tones can be activated from field-wired, normally open contacts, or a 24VDC external voltage source such as the output of a PLC. Normally open contacts can be obtained from the Cat. No. 5538-4 and/or Cat. No. 5538-4R Adaptatone Signal Actuators.