relay

the act of passing something along from one person or group to another; "the relay was successful"

a crew of workers who relieve another crew

a fresh team to relieve weary draft animals

a race between teams; each member runs or swims part of the distance

electrical device such that current flowing through it in one circuit can switch on and off a current in a second circuit

pass along; "Please relay the news to the villagers"

control or operate by relay