Traces circuit paths and wires on PCBs with components already in place. Has a probe voltage of only 0.2V, (far below the conduction threshold of all semiconductors), and a low input impedance (15 ohms for Model TZ, and 30 ohms for Model TZB) that eliminates all the false readings caused by measuring through a component. Two models to choose from. Model TZ, shown above, operates at 9V through a UL-approved 120VAC adapter (included), and features an ESD grounding jack for protection of static sensitive devices. Model TZB, not shown, operates on a 9V battery (not included). Both models give a clear audible signal over background noise, and come complete with test probes. The case measures 3-1/2" x 2-1/2" x 1-3/4".