Telephone Wiring Color Code - This document provides instructions for preparing a contract pricing proposal when certified cost or pricing data are required. Note 1. There is a clear distinction between submitting certified cost or pricing data and merely making available books, records, and other documents without identification.. On this layout, I use a system of "Bus" to distribute power supplies such as DCC, lighting models, turnout motors, electronic circuits, etc. . . Here, the "Bus"is a twisted pair of single strands wires 1.5 mm ², which runs along the entire layout..