A switching system that receives communications over a trunk incoming from a communications network and routes them to its subtending communications terminals responds to a stimulus, such as actuation of an actuator, by either (a) returning all of the communications that it receives on the incoming trunk at least subsequently to the stimulus to the network over a trunk outgoing to the network with instructions directing the network to redirect the returned communications to a second switching system for routing to communications terminals served by the second system, or (b) routing all of the communications that it receives on the incoming trunk at least subsequently to the stimulus to the second switching system over a trunk outgoing to the second switching system for routing to the communications terminals served by the second switching system.