This is a way of communicating on the half-duplex communication line, includes receiving and transmitting devices (walkie-talkie) by the way of pressing the button for switching to the voice mode or transition to the listening mode. It works as a radio speaker; one can talk by pressing the button and can listen to a voice message by releasing the button.
Level 3 (Nasdaq: LVLT) is an international communications and information services company and is headquartered in Broomfield, Colorado. The company operates one of the largest communications and Internet backbones in the world.