the neutral conductor could not be relied on to remain near ground potential; and, in fact, could be at full line potential (via transmission of voltage through a switched-on light bulb, for example). Modern electrical codes generally do not require a neutral fuse. Instead, they explicitly forbid configurations that might break continuity of the neutral conductor, unless all associated hot conductors are also simultaneously disconnected (for example, with ganged or "tied" circuit breakers). Advantages In the early 1900s, K&T wiring was less expensive to install than other wiring methods. For several decades, electricians could choose between K&T wiring, conduit, armored cable, and metal junction boxes. The conduit methods were known to be of better quality, but cost significantly more than K&T. In 1909, flexible armored cable cost about twice as much as K&T, and conduit cost about three times the price of K&T. Knob and tube wiring persisted since it allowed owners to wire a building for electricity at lower cost. Modern wiring methods assume two or more load-carrying conductors will lie very near each other, as for instance in standard NM-2 cable. When installed correctly, the K&T wires are held away from the structural materials by ceramic insulators. K&T wiring was commonly insulated with cotton cloth and soft rubber, in addition to the porcelain standoffs. Although the actual wire covering may have degraded over the decades, the porcelain standoffs have a nearly unlimited lifespan and will keep any bare wires safely insulated. Today, porcelain standoffs are still commonly used with bare-wire electric fencing for livestock, and such porcelain standoffs carry far higher voltage surges without risk of shorting to ground. In short, K&T wiring that was installed correctly, and not damaged or incorrectly modified since then, is fairly safe when used within the original current-carrying limits, about ten amps per circuit. Disadvantages Historically, wiring installation requirements were less demanding in the age of knob-and-tube wiring than today. Compared to modern electrical wiring standards, these are the main technical shortcomings of knob-and-tube wiring methods: never included a safety grounding conductor did not confine switching to the hot conductor (the so-called Carter system places electrical loads across the common terminals of a three-way switch pair) permitted the use of in-line splices in walls without a junction box (however, this downside is offset by the strong nature of the soldered and taped junctions used at the time). susceptible to damage in accessible