Battery:
              The most common form of nine - volts battery is commonly called the transistor battery introduced for the early transistor radios this is a rectangular prism shape with rounded edges and a polarized snap connector at the top this type is commonly used in pocket radios some detectors carbon monoxide detectors guitar effect units and radio controlled vehicle controllers.
 
 

                  They are also used as backup power to keep the time in certain electronic clocks this format is commonly available in primary carbon-zinc and alkaline chemistry in primary lithium iron disulfide and in rechargeable from in nickel-cadmium nickel-metal hydride and lithium-ion mercury oxide batteries in this form have not been manufactured in many years due to their mercury content.
          This type is designated NEDA 1604, IEC 6F22 and “ever ready” type pp3 (zinc-carbon) or MN1604 6LR1 (alkaline)
           Most nine-volt alkaline batteries are constructed of six individual 1.5V LR61 cells enclosed in a wrapper