A Logic Probe is a Low-Cost Hand-Held Test Probe used for Analyzing and Troubleshooting the Logical States (Boolean 0 or 1) of a Digital Circuit. When many signals need to be observed or recorded simultaneously, A Logic Analyzer is used instead. While most logic probes are powered by the circuit under test, some devices use batteries. They can be used on either TTL (Transistor-Transistor Logic) or CMOS (Complementary Metal-Oxide Semiconductor) Logic Integrated Circuit Devices, Logic Probe 50MHz TTL/CMOS & Pulse and etc.