This paper shows a possibility to visualize signal propagation in electronic circuits.Instead of using various galvanic measurement points all over the circuit, a test method is shown which measures the radiated field of the printed circuit board.By use of BIO JOINT a 2-dimensional positionable field probe it is possible to get an overview over tactical pen the signals running on the different parts of the PCB.In order to measure transient disturbing signals and distinguish them from normal device operation, problems of probe design and triggering need to be discussed.