The controlling switches _C C_ are provided with one and sometimes two handles, one of which is used to regulate the speed of the car and stop and start it, while the other is for the purpose of reversing the direction in which it runs. The handle _h_ is for the purpose of regulating the speed, and by means of _k_ the direction of motion is changed. Before _h_ is moved from the inactive position _k_ is turned so that the car may run either forward or backward, as may be desired; then, when _h_ is moved, the car will start, and by varying the position of _h_ the speed can be changed. If it is desired to reverse the car, _h_ is brought back to the stop position, _k_ is shifted to the reverse motion, and then _h_ is again turned to the running position. When the controlling switch is provided with only one handle this is turned in one direction to run the car ahead, and in the opposite direction to run it backward, the graduations in velocity being obtained by placing the handle in positions intermediate between the stop position and the highest speed position. As will be noticed, the wire _d d_ branches at _c_ and runs in both directions. Now, when the controller handles are both turned to the stop position the current from the trolley can get no farther than the ends of _d_ in either switch, but if one of them is turned to the running position, the current at once passes to the wires in the cable _e e e_, and thus to the two motors. If the switches _C C_ are in proper working order and there is no disarrangement of the wires leading to the motors or those within the latter, the current will obey the movements of the handle _h_, but under other conditions it may not. If such an emergency arises, the motorman reaches up to the hood and turns the safety switch _a_ or _b_, and thus cuts the current off. The force with which the motors turn the car wheels around depends upon the strength of the current; this is owing to the fact that the magnetic force is increased or decreased by variations in the current strength. If the current is doubled the magnetic force of the armature is nearly doubled, and so is that of the field magnet, therefore the pull between the poles is nearly four times as great. From this it will be seen that the force with which the car is pushed ahead can be increased enormously by a comparatively small increase in the strength of the current. If the current strength is doubled, the propelling force is practically quadrupled; and if the current is increased four times, the propelling force is made nearly sixteen times as great.