Channel Select Switch Used to switch between intercom channels one and two. The switch lights green for channel one and red for channel two.Intercom Listen Key Both momentary (push-to-listen) and latching (hands-free listen) are possible.Call Key Used to send call signals on the intercom channel and to indicate incoming calls.Intercom Talk Key Both momentary (push-to-talk) and latching (hands-free talk) are possible. Additionally, the WM-1000 / WM-2000 have a feature called "mic kill receive" which lets an operator at a remote master station (such as the US-2002) turn off the talk key.Dynamic-Mic Headset Connector 4-pin male XLR connector accepts headsets with monaural headphones and either a balanced or unbalanced dynamic microphone.Volume Control Adjusts intercom volume to headset.Audiocom / Clear-Com Selector Switch The selector switch sets the intercom station for compatibility with either Audiocom or Clear-Com channel connector pin-outs, channel power requirements, and call signaling requirements.Configuration DIP switches DIP switches are provided to enable/disable the following features: Call Beep: An optional call beep tone can be used for incoming call notification. Headset Microphone Type Selection: Balanced or unbalanced microphone may be selected. DC Call Enable: This may be turned on to use the intercom station with intercom systems that use DC call signaling.Connections Terminal Block Used to connect intercom channel(s) and an optional local power supply.Sidetone Trimmers These are used to adjust the level of the station operator''s own voice in the headphones.Mounting Holes The mounting holes fit any standard, two-gang electrical boxClear-Com Compatible