Then, as mentioned, the lamp takes turns to get gas from each furnace. The valves are connected to the dog gear wheels by a lever on the dial surface connected to the dog gear wheels, just as the dog gear wheels rotate. By looking at the lever on the dial surface, you can determine the amount of gas used in the home.
Electric meters contain electromagnets. An electric current passes through a telegraph cable wrapped around these magnets. When an electric current passes through it, the magnetic field from the magnet rotates a small shaft. The metal cylinder connected to the shaft also rotates. The shaft and the cylinder are connected to the arm on the dial surface.