Wiring

Data networks are more tolerant of data errors than CobraNet networks. Typical layer three and above protocols will retransmit and retry unsuccessful transmissions. CobraNet does not do this. By the time a dropped frame is detected, it is too late to retransmit; that isochronous cycle is gone. For this reason it is important to ensure the integrity of the wiring prior to commissioning. Data error rates that may go unnoticed on a typical data network cannot be tolerated on a CobraNet network.

• Make sure all cables are properly terminated.
• Do not use kinked cables. If a cable is kinked during installation, do not straighten it out; use a new cable. The sensitive internal wiring twist which influences noise rejection and maximum data rate has been damaged.
• Do not run cables parallel to AC mains lines.
• Do not run cables close to noise sources, such as motors, fans, compressors, dimmer circuits, A/C lines etc..
• If running longer links or in noisy environments, use optical fiber.
• Use Cat 5e or above for copper 100 BASETX links.
• Use Cat 6 for copper gigabit links when copper must be used. Use fiber instead of copper on gigabit links whenever possible. The way in which data is modulated on gigabit copper makes it more sensitive to outside interference. Therefore, when copper gigabit links must be used, pay particular attention to cable routing and ensure that the cables are not in proximity to any potential noise or interference sources. A data integrity problem on a gigabit link may go unnoticed on a data network but will cause audio dropouts on a CobraNet network.
• If possible, perform bit error rate tests on each link and correct problems before commissioning.
• Check switch statistics for indications of errors and dropped or malformed frames. Find the root cause and correct it before commissioning.
• Do not exceed the maximum recommended run length of the media in use, i.e. no more than 100 meters for copper Ethernet cables. Fiber run lengths can vary depending on cable and switch manufacturer. Typically lengths of no more than 2 km are recommended for 100 megabit multimode fiber, 600 meters for gigabit and 300 meters for 10 gigabit. Single mode fiber supports much longer runs but is also more expensive and seldom used in LAN applications. Consult the documentation for the particular equipment and wiring used in order to ensure maximum lengths are not exceeded.

  Note: A large CobraNet network can sometimes be complex to commission. Make sure the systems contractor only has to focus on his own tasks and does not have data integrity issues to debug as well. Ensure that the network is operating as required before handing it over to the contractor.