circulator

Noun

 * 1) A person or thing that causes something to circulate
 * Who is the circulator of this rumor?
 * 1)  A local transit system that provides regular service within a closed loop
 * You can ride the airport circulator to the next terminal.
 * 1)  A passive electronic component with three or more ports, in which the ports can be accessed in such a way that when a signal is fed into any port it is transferred to the next port only

Etymology
From.

Noun

 * 1) itinerant peddler or performer
 * 2) mountebank, quack

Etymology
, from. Equivalent to.

Adjective

 * 1) circulatory