Demystifying Twisted-Pair Cable Connector Types
Have you ever wired a cable directly into a piece of hardware? Some equipment in the past years provided terminals or termination blocks so that cable could be wired directly into a direct component. At the ends of the cables you install, something must provide access and transition for attachment to system electronics. Thus, you need connectors.
Connectors usually have a male component and a female one, except in the case of hermaphroditic connectors such as the IBM data connector. Jacks and plug are usually systematically shaped, but sometimes they are keyed, which means that they have a unique, asymmetric shape or some system of pins, tabs and slots that ensure that the plug can be inserted only one way in the jack. This article covers three types of connectors you may encounter when working with structured cabling system.
Many people in the cabling business use twisted-pair connectors more than any other type of connector. The connectors included the modular RJ types of jacks and plugs and the hermaphroditic connector employed by IBM that is used with shielded twisted-pair cabling (ie. cat6 shielded cable). What is equally important as the cable connector is the connector used with patch panels, punch-down blocks, and wall plates; this connector is called an IDC (insulation displacemeny connector).
Most unshielded twisted-pair (UTP) and screened twisted-pair (ScTP) cable installations use patch panels and, consequently, 110-style termination blocks. The 110-block contains rows of specially designed slots in which the cables are terminated using a punch-down tool.
Solid vs. Stranded Conductor Cables UTP and ScTP cables have either solid copper conductors or conductors made of several tiny strands of copper. Solid conductors are very stable geometrically and therefore electrically superior, but they will break if flexed very often. Stranded conductors are very flexible and resistant to bend-fatigue breaks, but their cross-sectional geometry changes as they are moved, and this can contribute to electrical anomalies. Stranded cables also have a higher attenuation than solid-conductor cables.
The differences in conductors mean a difference in IDC types. You have to be careful when purchasing plugs, wall plates, and patch panels because they won’t work interchangeably with solid- and stranded-core cables because the blade designs are different.
Twisted-pair cables are most commonly available as UTP, but occasionally, a customer or environmental circumstances may require that ScTP cable be installed. In an ScTP cable, the individual twisted pairs are not shielded, but all the pairs collectively have a thin shielded around the shielded of foil around them. Both UTP and ScTP cables use modular jacks and plugs. For decades, modular jacks have been commonplace in the home for telephone wiring.
Modular connectors come in four-, six-, and eight-position configurations. The number of positions defines the width of the connector. However, many times not all of the positions have metal contacts installed. Make sure that the connectors you purchase are properly populated with contacts for your application. Note the metal shield around the jack; it is designed to help reduce both EMI emissions and interference from outside sources, but it must be connected properly to the cable shield to be effective. The following figure shows an eight-position modular plug for UTP cable.
Shielded twisted-pair connectors go with the shielded twisted-pair cable which encases the signal-carrying wires in a conducting shield as a means of reducing the potential for electromagnetic interference. How effective the shielding is depends on the material used for the shield--its thickness and frequency, the type of electromagnetic noise field, the distance from the noise source to the shield, any shield discontinuity and the grounding practices. Please note that the crosstalk and signal noise can increase if the effects of the shield are not compensated for.