| 摘要 |
<p>A method and apparatus for providing for communication over a public switched telephone network (PSTN), between an alarm device 20 and a remote device such as an alarm gateway, polling server or alarm receiving centre. The alarm device is of the type which communicates using the dual tone multi-frequency fast format (DTMF FF) protocol. An interface device provides for peridically sending a test signal to a remote monitoring device so that the remote monitoring device can verify integrity of a communications link between the interface device and the remote monitoring device by detecting a fault if the test signal is not received within a predetermined period.</p> |
