BW 40.28 230V Hour Counter, 5 digits, Screw Connection, 230 V ac. The Muller BW40 series, a motor-driven hour meter is 5-digit analogue display, panel mount device. It has a supply voltage rating of 230VAC. It is supplied with a panel clip and bezel for mounting through a 50mm diameter hole. It has a meter accuracy of 0.01 hours.