The Time Mark 208A & 208D Line Voltage & Phase Sequence Detectors allows quick and easy determination of phase sequence (either ABC or CBA). Available in 50/60 Hz and 400 Hz versions, this unit can also show that all phases are present, or if one or more phases are lost, it indicates which of the phases are missing. To use, connect the Detector to any 3-phase circuit, Wye or Delta. In proper phase sequence, and with all phases present, the ABC lamp, and the three line voltage lamps will illuminate. An open phase condition will illuminate both rotation lamps and only two line voltage lamps.