headlamp hl 2 turned off this is because the voltage increase on the system and thus on headlamp hl 1 more than compensates for the lost output of headlamp hl 2 it should be understood that switch s 2 is not a mechanical switch operated by the operator but some automated switching method such as a solid state switch controlled by the voltage or frequency or the instantaneous change of voltage with time present on the electrical system the switching function identified as s 2 as above described is an optional part of the new components now to be described in fig2 the rest of the circuit may function without the switch s 2 or the functions just described switch s 2 may function without the rest of the circuit components if scr 1 is gated on then it can be described as functioning like a diode and in that case capacitor c 1 diode d 1 amp scr 1 will function as a known voltage doubler circuit capable of producing an output voltage across filter capacitor c 2 and thus the speedometer this voltage can be greater than the zero to peak voltage of the alternator a the voltage control circuit removes.