Telephone exchange having line status signals replaced by audio signals such as advertisements

摘要

A telephone exchange comprises control means responsive to one or more call-progress conditions of a first subscriber line to link to the first subscriber line an audio signal source selected in respect of the first subscriber line from a plurality of such sources. The control means are operable to identify a predetermined association between at least one of the audio signal sources and a respective second subscriber line. The control means are operable further, in response to a predefined trigger signal dialed from the first subscriber line, to identify a second subscriber line associated with the selected audio signal source and to initiate a call attempt from the first subscriber line to the identified second subscriber line.