Overvoltage protection Glitel GAP050 type of SPD T3 with switching direct-current adapter 12V/2A is used for protecting electrical and electronical devices against impulse overvoltage from electrical network 230V/50Hz (TNS, TNC, electrical socket type E, F) and also for protection of telecommunication devices connected to analog telephone line against impluse overvoltage from telecommunication line. Solution of Glitel GAP050 does not influence DSL transfer data speed to 100Mbps.