In the day mode, the Viking TMS-2 Two Line Call Sequencer answers calls on one line while you are busy or on the opposite line. After a professional greeting has been played, it holds the caller for Up to 15 minutes or until you are available to take the call. Music on hold can be provided from a radio or any other audio source.In the night mode, It allows your answering machine to answer either line. The LED indicator displays which mode is active (day or night) and which line is on hold. A volume adjustable beep and warble also indicate which line is on hold or ringing.