Which instrument is best suited for checking a TTL logic circuit?

A logic probe is specifically designed for checking TTL (Transistor-Transistor Logic) logic circuits. It can indicate the presence of high or low logic levels, which are crucial for diagnosing the state of digital circuits. The logic probe provides visual feedback, such as lights or sound, depending on the logic level it detects. This enables technicians to quickly determine whether a particular point in a TTL circuit is functioning correctly and whether the signals are traveling properly.

In contrast, while a multimeter can measure voltage levels, it is not well-suited for real-time analysis of fast-changing digital signals typical in logic circuits. Similarly, an oscilloscope, although very capable of viewing waveforms and analyzing signal shapes and timing, might be more complex to use for simple low/high status checking of TTL circuits compared to a logic probe. A signal generator is primarily used for producing specific signals and is not meant for testing or diagnosing existing circuits. Thus, for checking TTL logic levels specifically, the logic probe is the most appropriate instrument.