Telecommunications networks

摘要

A telecommunications network includes digital main switching units and local exchanges. The local exchange is arranged to permit alternative alert signals to consumer premises by way of the local loop. The alternative signals may be cadenced to provide information to apparatus connected in a consumer's premises without causing activation of traditional telephone, facsimile or answering machines. Such information may be supplemented by the presence or absence of a line polarity reversal before the activation signal is sent and by modulated signals, such as FSK signalling.