Bus coupler for coupling 2 bus supplies (bus districts). The bus coupler transmits bus telegrams from one bus district to the other and vice versa. Bus short circuits are detected and not transmitted. Mains connection, output side: 2 x bus connections. The connections are made via screw terminals. Control cabinet housing made of flame-retardant polycarbonate, halogen-free, suitable for mounting on 35mm top hat rail, in accordance with EN 50022, permissible ambient temperature from 0 to +50°C, protection class IP20, dimensions: 140 x 90 x 59mm, 8 HP each 17.5mm.