Understanding 120/240V Wiring Color Code | DoItYourself A Word of Caution: Always use a line voltage meter or circuit tester to determine if a wire is "hot" or "live." Never rely on a wire's color alone. Wiring Types. Depending on where you live, the branch circuit wiring in your home will be made with individual conductors run through hollow metal conduit, or with one of three types of cable.Author: DIY Staff Screw-In Plug Fuses, Tamper-Proof Fuses, and Fuse Adapters Screw-in plug fuses are found on old home wiring systems that include a fuse panel instead of a modern circuit breaker panel. Most of the fuses in a fuse panel are screw-in type, while circuits for large electric appliances, like ranges and clothes dryers, may have cartridge-type fuses.