# Using call diversion services (Q.SIG)

Q.SIG describes interactions between nodes in a network. This section describes how call diversion services work from three perspectives:

- The node that makes the call (the originating node)

- The node the call is originally addressed to (the served user node)

- The node the call is diverted to (the diverted-to node)

Originating, served user, and diverted-to nodes

Note: The application layer must participate in the diversion by interworking the events on the A<->B and A<->C legs of the call.

The following illustration shows the call diversion service in the NMS ISDN Q.SIG implementation (from the originating user's perspective):

Call diversion service in the Q.SIG implementation