Which instrument is used to indicate high and low digital voltage states?

A logic probe is a specialized instrument designed specifically for evaluating digital circuits by indicating high and low voltage states. When a logic probe is connected to a point in a circuit, it will provide visual or audible indications of whether the voltage at that point is above or below a defined threshold, thus representing digital '1' (high state) or digital '0' (low state).

In digital electronics, where signals are represented by binary states, it is essential to quickly assess these states for troubleshooting or analysis. The logic probe is particularly useful because it provides immediate feedback about the digital state without the need for complex measurements or setups.

Other instruments listed, while useful in their respective roles, do not serve this specific purpose as effectively. A multimeter can measure voltage, but it does not provide real-time indications of digital state changes in a manner that is as immediate and accessible as a logic probe does. An oscilloscope can display waveforms and provide detailed visual insights into signal changes over time, but it requires more setup and interpretation. A signal generator is used to generate test signals, not to measure or indicate the state of existing signals. Thus, for the purpose of indicating high and low digital voltage states directly, the logic probe is the most appropriate instrument.