Wiring Colors Meaning - Buy Genssi 30/40 AMP Auto LED Light Bar Relay Wiring Harness SPDT 12V 40A (10 Pack): Relays - Amazon.com FREE DELIVERY possible on eligible purchases. Electrical Computer-Aided Design Consulting for AutoCAD, AutoCAD Electrical 2017, Toolbox/WD, VIA/WD, and Promis-e. Industrial controls design specialists, including schematic, wiring diagram, bill-of-materials, wire from/to list, and panel layout, since 1988. Experienced with DIN, IEC, AS, and U.S. standards. AutoCAD Electrical training courses and training material, including on-site. A modular connector is an electrical connector that was originally designed for use in telephone wiring, but has since been used for many other purposes. Many applications that originally used a bulkier, more expensive connector have converted to modular connectors. Probably the best known applications of modular connectors are for telephone and Ethernet..