Abstract: A procedure and a system for the detection of a plurality of passive electronic markers are disclosed. A marker location device capable of scanning for multiple types of electronic marker thereby increasing operator efficiency and reducing erroneous marker indications is described. In some embodiments, scanning may be performed at the operating technician's direction or may be performed in the background while the operating technician is performing other tasks.

Abstract: A multitude of alarm indicators are layed out in a signal line for the purpose of monitoring an extensive object. Such an object can be a large building, a pipeline or similar device. In order to determine which of the alarm indicators has triggered off the alarm, a repeated pulse is fed into the signal line whose echo is compared with a programmed-in echo signal. The programmed echo signal is acquired through the transmission of a pulse when all of the alarm indicators are out of service. By comparison of the programmed-in echo signal with the measured echo signal, the distance of the activated alarm indicator from the beginning of the signal line can be measured.