A surge protector for single-phase or multi-phase power lines is disclosed, for permanent connection near the entrance of power lines to a building, that has a basic protector sub-circuit of a metal-oxide varistor (MOV) and a gas-discharge tube (GDT) connected in series between the power line and building...http://www.google.co.uk/patents/US6778375?utm_source=gb-gplus-sharePatent US6778375 - Hybrid MOV/gas-tube AC surge protector for building entrance
