What type of control is typically used for the variable range marker?

The correct answer is a variable resistor, as this type of control is commonly utilized for adjusting the variable range marker in various electronic circuits, particularly those involving radio frequency (RF) and communication equipment. Variable resistors, or potentiometers, allow for fine adjustments of resistance, which can directly influence the voltage across a portion of the circuit. This capability is essential for calibrating instruments that display or utilize range markers, enabling the user to set desired frequency ranges or levels.

In the context of the variable range marker, the ability to make precise adjustments with a variable resistor can facilitate the tuning process, making sure that readings or output correlate accurately to the intended operational parameters. This level of control is vital in ensuring the fidelity of signal processing and reception in communication systems.

Other options, while they have their own specific applications in electronics, are less suited for this function. For example, variable inductance and variable capacitance are typically employed in tuning circuits and oscillators, where adjustments influence frequency characteristics rather than marking ranges. A variable resolver, on the other hand, is mainly utilized for position sensing and feedback in control systems, which is not aligned with the requirements of controlling a variable range marker.