Who is in charge of the Change in Ticker Price?

by Don
(Illinois)

I have watched ticker tapes and currency tickers change
faster than a bolt of lighting and i am amazed and do
not understand how it's possible.

My Question is this:

How can thousands of prices on ticker tapes change so
fast? Who is in charge of the switch? The numbers has
to be coming from somewhere' It seems impossible for
this to be happening without someone calling the shots.

Are the people in charge of the tickers allowed to
invest?

Amazed in Illinois.