The W-SD is a Star-Delta timer. Specially designed for induction motor starting, the star-delta transfer time is set to 0.06s or 0.1s with the star-delta transfer time selector on the lower-right side of the front panel. When input voltage is available, the relay star will energize and star time period begin the timing cycle. At the end of the timed period, the relay star will be de-energized, the adjustable delay star to delta period start. At the end of the transfer timed period, the relay delta will energize. When input voltage is removed, the timing circuit is reset and both relays (Star-Delta) are de-energized. Two relay outputs for Star and Delta. Fit standard 8 pin sockets.