PP3 Battery 9V Alkaline

9V PP3 alkaline battery, also known as NEDA 1604, IEC 6F22, 6LF22, 1604A or MN1604 6LR61. 

This common nine Volt battery is sometimes called the "transistor battery", as it was originally introduced for the early transistor radios. 

Commonly used in pocket radios, smoke detectors, carbon monoxide detectors, guitar effect units, electro-acoustic guitars and radio remote controlled vehicle controllers. 

They are also used as backup power source to keep the time in some electronic clocks.