Cable trays are a support system for electrical cables, power, signal, and communication and optical fiber cables. This issue of the CableGram presents questions and CTI answers to these questions that have been asked by interested persons and organizations concerning the application of cable tray systems. We believe you will find the answers useful. Here's what you need to know: Cable Types: Only use. en completely installed, without damage either to conductors or structural system use maintain spacing or to keep cables in place when the tray is ect the minimum bend ra-dius for cables as they exit the bottom of the cable tray. A rung spacing of 6 to 9 inches (150 to 230 mm) is preferable when. Cable tray types, fill rules for single-conductor and multiconductor cables, ampacity derating, separation requirements, and when to use tray vs conduit.