I know this question has been raised previously but as a newcomer to electronics there is still a bit missing for me. As I understand it the small base current allows a larger current to flow through the transistor. So if we need the base current to flow to allow the transistor to operate as a switch, what turns the base current on? If that is another switch, what is the point of the transistor as a switch in the first place, why not just use a mechanical switch?