Abstract: A method and system for responding to security system inoperability due to damage of a telecommunications line interconnecting the security system to its central monitoring service system requires origination of a wireless telephone call. A wireless unit is interconnected to the security system and originates an emergency call upon detection of telecommunications line abnormalities. Upon establishing a call connection between the wireless unit and the central monitoring service system, the wireless unit relays dual tone multifrequency (DTMF) signals which identify the security system affected by the breach so that appropriate authorities may be dispatched. In alternative embodiments, the wireless unit is programmed to place calls to other designated telephone numbers.

Abstract: A method and system for providing redundancy for security systems served by the public switched telephone network (PSTN) includes a cable modem interconnected to a security system controller. Upon detection of inoperability of a telecommunications line serving the system via the PSTN, the cable modem extends an alert message to a security monitoring service via a packet data network. Advantageously, the cable modem can also send video images and audio from the secured premises to the security monitoring system due to the bandwidth capabilities of the packet data network.

Abstract: Resistive circuits are provided at the tip and ring of the battery feed circuit as a method of alleviating the need for bulky DC transformers or complex integrated circuitry. The voltage is monitored through a set of comparators eliminating the expense of maintaining fused resistors. The voltages for voice or data transmission is amplified prior to being transmitted. Received signals are AC coupled, with proper biasing, onto the tip and ring lines. Any AC noise on the tip and ring line is shifted 180 degrees out of phase and re-inserted on the line to cancel the noise. As an enhancement to the battery feed circuit, another voltage comparator is added to check the line for DC current signifying an off hook condition.