Technical Discussion

AntiTheft Power Cord and Alarm Networking

Prof. Glenn Chapman, Simon Fraser Univ.
V1.0, Aug. 28, 2005


The Anti-theft power cable prevents theft of electrically powered apparatus by detecting the physical removal of the equipment’s power plug from an electrical power outlet. As each piece of equipment has its own anti-theft power cable they are individually protected. Yet the overall design/patent includes several methods that can be used to create a networked system, the monitoring of which can alert a central station about equipment being removed from it’s home outlet.

Anti-theft power cable networked Alarm

Since each protected piece of equipment can generate a unique alarm that can be used by the base station. Base stations have been created that can detect the alarm state and transmit the alarm to a wider area monitoring system. In one already implemented network, an acoustic detector watched for the specific alarm signal from a power cord. In this monitored system, a two tone alarm of specified durations for each machine was used. A simple microprocessor based acoustic area station detection system can identify and separate the different alarms from any background sound levels. Upon detection of an alarm the area station forwarded an alarm notice by dialing a preset phone number and announcing the alarm condition and the location of the alarm. This has also been done using a voice announcement for a human operator.

The same system can be modified to send a modem or internet signal to a security computer. In the audio range sound alerts it would be easy to generate a low frequency ultrasonic signal that is silent if desired. Alternatively for a modest cost (about $2 per cable) a wireless signal using a ZigBee wireless network can be implemented that would allow a radio frequency base station alarm to be used.

Advantages over other networked Alarms

The anti-theft power cord has an important advantage over other network monitored theft prevention systems. Those systems require the equipment communicate to some central monitoring station. This means in those systems there is a single failure point which disables the theft detection. For example power line detection systems that depend on detecting current drawn by equipment and communicating over power lines, can be bypassed by cutting power to rooms or building. Wireless based systems that detect equipment movement have the same problem – cutting power or jamming the wireless signal removes the detection. In the case of the Anti Theft Power Cord, as each power cord protects its own equipment with an alarm state, the area monitor is an added level of alarm notification and protection that operates separately to provide rapid response.