Abstract: In a communications system (100), a network access device (102) is coupled to a packet network (104) and a circuit-switched network (106). User terminals (112, 130) coupled to the network access device make requests for network access. The network access requests may include data indicating which network is required for a call. This is particularly useful for user terminals that need a certain level of reliability for a call, for example, TTY/TDD devices. A processor (124) in the network access device (102) determines whether each request for network access includes a request for one of the circuit-switched or packet network (202). If the request for network access identifies one of the networks for the call, that network is used for the call, if it is available (208, 212, 214). A fast busy is used as a failure notification to the user terminal (112, 122) if the selected network is not available (210).