What is a characteristic feature of a terminal block?

A terminal block is designed primarily for ease of wiring connections in electrical systems, and one of its defining characteristics is that it is both modular and insulated. Being modular means that terminal blocks can be assembled in various configurations, allowing for flexibility and scalability based on the specific requirements of a project. This modular nature makes it convenient for electricians and engineers to customize their wiring setups efficiently.

Insulation is also a key aspect, as it helps prevent accidental contact with live wires, reducing the risk of shorts and enhancing safety. Insulated terminal blocks ensure that conductors are safely housed and that there's minimal risk of electric shock or arcing during operation or maintenance.

The other options do not align with the fundamental functions of terminal blocks. Converting AC to DC, signal amplification, and voltage regulation are not features of terminal blocks; these functions are typically handled by specialized devices such as rectifiers, amplifiers, and voltage regulators, respectively. Therefore, the correct identification of terminal blocks as modular and insulated highlights their primary roles in electrical installation and safety.