There is provided an instance of a client application enabling a first user terminal to access a packet-based communication system to conduct voice or video calls over a packet-based network. The client application is configured to receive an input from one or more audio and/or video input transducers of the first terminal, and to operate in conjunction with one or more other instances of the client application executed on one or more respective second terminals so as to participate in an analysis of the one or more inputs in relation to an input from one or more audio and/or video input transducers of the one or more second terminals; thereby enabling selection of one of the first and second terminals for use by a near-end user in conducting a call with a far-end user of a third user terminal via the respective client instance and packet-based communication system.
