TeSys U phase barrier for use with power bases LUB12, LUB32, LUB38, LUB120, LUB320, LUB380 or a limiter block LUALB1. It ensures a complementary electrical insulation between phases. Compulsory for use with a 690V AC network and with a 440 V AC network when assembling a UL508 type E compliant motor starter (Self Protected Starter).