circulator

noun3

1. •
   A person or thing that causes something to circulate

   • Who is the circulator of this rumor?
2. •
   A local transit system that provides regular service within a closed loop

   • You can ride the airport circulator to the next terminal.
3. •
   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