The unit consists of 2 meters- one Voltmeter of 10V & another Milliammeter of 150 mA. Three resistance R ,12 3 R & R (of the order of 50 ohms each Connected in series. Voltmeter 10V is mounted in box| with their independent sockets. Milliammeter of 150mA is connected in series with all the three resistances & external input terminals. Built in DC regulated powersupply of 10V, 500mA.