KT-100L is a professional electronic hearing stick with filter. It adopts high integration circuit. It has high reliability, handiness, compactness, easy to carry, flexible and simple to operate, economical and practical. With the traditional mechanical type to drain rod compared to the electron leakage listening bar adopts the high sensitivity of the piezoelectric sensor has higher sensitivity, through multistage filter, the maximum removal of noise, the leak sound more clearly. The utility model is convenient for inserting grassland and soil detection, and is suitable for all kinds of road census listening in a long time. Suitable for all kinds of pipes including plastic pipes.