Abstract: A method and system of monitoring a premises includes testing a digital data link between a Signal Point and a monitored premises, generating an interruption signal to identify any interruption in the data link, generating and transmitting a trouble signal from a processor at the SP to a central monitoring center in response to the interruption signal and then sending a restoration signal from the processor means to said monitoring center when the data link has been restored. The data link means may be part of an ISDN or SS7 network, and the restoration signal may be generated in response to the monitored premises signing-on to the Signal Point.

Abstract: A Public Switched Telecommunications Network (PSTN) including trunks connecting SPC switches and having a common channel signalling network with SPs, STPs, and SCPs, with each of the SPs connected to an MCC which is connected to an MMOC forming part of an SCC which includes a critical indicator panel which mirrors system alarm signals at the MCC. Connected to the PSTN is a monitoring center associated with monitored premises having sensing devices connected to an interface at the premises. The interfaces and SPs are connected by two full duplex channel data links which are continuously subjected to loop back testing which is connected to provide at the MCC an alarm signal to identify any interruption in the communication through the SP and trunks connected thereto and also to provide at the MCC a signal of interruption of a data link connected to the first SP. An adjunct processor is provided at an SCC connected to a plurality of MCCs.