Telephonic communications – Diagnostic testing – malfunction indication – or electrical... – Monitoring
Patent
1997-12-15
2000-01-11
Loomis, Paul
Telephonic communications
Diagnostic testing, malfunction indication, or electrical...
Monitoring
379 34, 379 37, 379142, H04M 124, H04M 1104
Patent
active
060144262
DESCRIPTION:
BRIEF SUMMARY
This invention relates to telephone line monitoring and more particularly, but not exclusively, to the monitoring of a telephone line between a subscriber's equipment and a central monitoring station.
Types of subscriber equipment which may be monitored by a central station may be of various kinds. Usually the line connection is via the Public Switch Telephone Network (PSTN) although other telephone lines may also be used. The subscriber's equipment may comprise, for example, a device for providing an electrical signal when an abnormal condition is detected at the subscriber's premises, such as, for example, afire, an unauthorised entry, or a malfunction of machinery under surveillance. Alternatively, the device may provide an electrical signal indicative of the state of certain equipment at the subscriber's premises on a routine bases. For example, the device may monitor utility meter readings, meterological measurements, or the operational data of process equipment. The invention will hitherto be described in connection with the monitoring of a telephone line between an alarm system and a central monitoring station, but it will be understood that the invention is not limited thereto, and could be used to monitor a line carrying electronic data between a central station and any of the abovementioned types of subscriber equipment, or between several pieces of subscriber equipment without the use of a central monitoring station.
When an alarm system is installed in a subscriber's premises, the premises are graded dependent upon the potential risk and the value of the property to be protected. If the premises are classed as medium grade or above, a digital communicator is fitted to the alarm system control panel. When the panel is operational, should the alarm be activated, the digital communicator will call a central monitoring station and transmit the status of the alarm system. In conventional systems, the digital communicator relies solely on the telephone line, and if this is cut it has no way of informing the central station and the central station has no way of monitoring the digital communicator. In order to overcome this problem and to monitor the line integrity, it would be possible to arrange for the digital communicator to call the central station on a periodic basis and inform the central station of its status. However, to achieve a reasonable level of monitoring, the digital communicator would need to call the central station, for example, about every ten minutes. The call charges for operating such a system would be prohibitively expensive.
An improvement on the above system has been introduced, which, in the UK, is called the British Telecom RedCARE System. This uses an existing telephone line to provide a secure communications link between the alarm system at the protected premises and the central monitoring station. To facilitate security, two modes of communication are employed a continuous inaudible low frequency tone, normally present all the time, and an audible "chirp" used to transmit alarm messages and check for the presence of the digital communicator. The "chirp" is an FSK (Frequency Shift Keying) modulated signal and contains information about the status of the alarm system. In installing such a system, it is necessary for the telephone exchange to be informed, and for the appropriate connection at the exchange to be made, to enable correct operation of the system. The telephone line used to monitor the alarm system may be used for voice communication, but cannot be shared with modems or fax machines. The digital communicators required for the RedCARE system are two to three times the pride of conventional digital communicators and the charges for using the RedCARE system are more expensive than standard telephone charges.
The installation of such a RedCARE system is described in a brochure entitled EUROSTU Installation Guide published by Versus Technology Limited of Aldershot, Hants. The operation of the system is described in UK patent application no. GB2115651. The entire discl
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patent: 5546448 (1996-08-01), Caswell et al.
patent: 5684858 (1997-11-01), Hartmann et al.
Copy of International Search Report dated Jul. 12, 1996.
Drysdale Andrew James
Herrera Juan Sebastian
Loomis Paul
Pyronix Limited
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