A probe for developing a visual indication of the electrical state of a selected point in a digital circuit under test. The probe is provided with two clips for attaching to the power supply and the ground of the circuit to be tested. The operator then holds a sharp tip of the probe at the selected point at which the electrical condition of the circuit is to be tested. Two light emitting diodes visible on the probe body display which one of the six possible circuit conditions exist at the selected point, such as open circuit, positive-going pulse, negative steady-state and so forth. The circuit utilizes integrated circuit NOR and inverting buffer components. Pulses as short as ten nanoseconds may be detected. The probe may be used with any voltage range of the various logic circuit families.