What is open wiring on insulator?

Open wiring on insulator refers to a specific wiring method that historically involved the use of cleats, knobs, and flexible tubing to support the conductors. This method typically consists of uninsulated conductors that are secured to a surface through these supporting devices, allowing for the conductors to remain safely distanced from surfaces that could potentially cause short circuits or other electrical hazards.

This technique has roots in older electrical installation practices and was commonly used for above-ground wiring in residential and commercial applications, particularly where insulation methods available at the time were less effective than modern standards. The support provided by cleats and knobs ensures that the wires are held in place, reducing the risk of physical damage and maintaining the integrity of the electrical system.

In contrast, the other choices describe different methods of wiring and installation that do not align with the definition of open wiring on insulator. These alternatives highlight aspects such as underground installation, conduit systems, or methods involving exposed but insulated wiring, which do not pertain to the characteristics of open wiring on insulator as defined in the question.