We report here a single pulse selector which is a high voltage pulsed switch using a Blumlein circuit and a krystron with either electric triggeror laser light trigger. A Poekels cell is made of longitudinal z-eut LiNbO3. The switching efficiency is about 50%. The light extinction ratio is more than 1000:1. The halfwave voltage is 3.2kV, delay time of the switch is 30-60ns. The device has operated for a long time at a repetition rate of 10 Hz with reliable performances.