A dynamo is an obsolete electrical generator that creates direct current using a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
How is it the least reliable? It contains highlight from the books and sites on the Internet, a good citation page is better to take information from than anything else. The only bad thing is if the other sites have wrong information or the site itself isn't citated much