Federal Signal's AudioMaster 310-MV is an industrial intercom that provides reliable two-way communications and superior sound quality. This unit has a rugged Type 4X housing and is UL Listed and CSA Certified. The AudioMaster 310-MV's standard features include volume control, call button, balanced line output, dust- and water-tight housing, listen/talk switch, remote device activation and the ability to power another intercom at 24 VDC. This heavy duty intercom will operate from -31 to 150 deg F in both indoor and outdoor applications. Remote device activation allows you to activate an auxiliary signal such as a horn or light. The AudioMaster 310-MV intercom is easy to operate. Press the toggle switch to talk and then release to listen. Additionally, press the call button to get the attention of personnel at another intercom.