BS 8521:2009

This standard BS 8521:2009 Specification for dual-tone multi-frequency (DTMF) signalling protocol for social alarm systems is classified in these ICS categories:

• 13.320 Alarm and warning systems

This British Standard specifies requirements for the transfer of information and controls within a social alarm system, by means of dual‑tone multi‑frequency (DTMF) tone signals passing between site control or local equipment and an alarm receiving centre via the public switched telephone network (PSTN) supporting voice traffic conforming to ITU‑T Recommendation G.711 [1].

The standard specifies an in‑call protocol which supports the 300 ms maximum round trip delay specified in the UK National Transmission Plan [2] for connections over the fixed network.