Developments, applications of and experiences with a digital processed microphonic cable sensor

In the late 1970s the first microphonic cable detection systems for fences appeared on the market. In comparison to existing fence sensors built in solid housings already on the market at the time, these systems had many advantages, e.g. they were simple to install, highly reliable with high performance and good value for money. Developments in technology over the years has lead to various microphonic cable developments on the basis of different technological and physical principles. However, the performance of all these systems was restricted by the very simple analog evaluation principles used by different manufactures. Sensitivity was adjustable but not defined, and the detection to false alarm ratio was rather an accidental result of a longer testing period. In 1993 the PERIFON-M(R) system appeared on the market. It was the first microphonic sensor based on digital evaluation principles. Its automatic adjustment to any fence structure represents a significant breakthrough in solving the various problems mentioned above. This paper will describe the processing principle, integration of various fence structures, automatic sensor adjustment, detection, false alarm recognition, the performance and maintenance program, intercommunication using a portable PC and finally the experience with the system over the last three years.