circulator

noun

1. A person or thing that causes something to circulate

- Who is the circulator of this rumor?

2. (transport) A local transit system that provides regular service within a closed loop

- You can ride the airport circulator to the next terminal.

3. (electronics) 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