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In decades past, cabling for voice and data communications systems was far less complex than it is today. Most systems used two-pair or four-pair copper wire sheathed in a binder to protect the cable. Connections often involved stripping off the end of the wire to expose the copper conductor. This was then attached to a set of connectors, usually called a connecting block, which connected physical devices to a switching apparatus, such as a PBX system.
With the growth of digital transmission in virtually all kinds of voice and data communications equipment in the late 1970s and early 1980s, new types of wiring and connectors emerged. The idea was to simplify the process of connecting devices to their primary system, hopefully speeding up the process of building a wired infrastructure for both voice and data devices.
What is a structured cabling system?
As wiring and connection points evolved, more standardization was needed for cabling, connectors and the different types of wiring, including copper, fiber and coaxial. The American National Standards Institute and Telecommunications Industry Association set forth a series of standards, ANSI/TIA-568, to introduce guidelines for all aspects of residential and commercial building cable distribution systems.
These standards shape the structured cabling system. Structured cabling is based on six components that, together, provide a convenient, repeatable and easily implemented framework for installing telecommunications cabling. The six components of structured cabling are the following:
- Entrance Facilities
- Equipment Room
- Backbone Cabling
- Telecommunications Room
- Horizontal Cabling
- Work Area
Why is structured cabling important?
Structured cabling greatly simplifies the installation of a cable infrastructure that supports a wide variety of voice and data communications equipment. Whether installing a coaxial outlet in a home or wiring a skyscraper, the components are all made to specific standards for electrical transmission, resistance, cable lengths, connectors and cable fabrication.
Structured cabling also enhances troubleshooting of wiring problems when using the proper diagnostic equipment, which is designed to be compatible with the ANSI/TIA-568.0/1 standards. Installation is also easier with structured cabling because the interfaces are standardized, typically using snap-in connectors.
Structured cabling standards
The development of structured cabling systems was greatly helped with the release of the ANSI/TIA-568 standard in 1991. Its sections included Generic Telecommunications Cabling for Customer Premises (C.0) and Commercial Building Telecommunications Infrastructure Standard (C.1). The two standards have been updated numerous times in the past 30 years, and the current iterations are ANSI/TIA-568.0 (customer premises) and ANSI/TIA-568.1 (commercial buildings). Both were most recently updated in March 2020.
Structured cabling benefits
The installation, troubleshooting and maintenance of cable infrastructures are greatly simplified with structured cabling. This saves money through standardization of all hardware components and cable types. It also saves time with installation as connectors and their wiring are greatly simplified. The ANSI/TIA-568 standard is adaptable to virtually any kind of residential and commercial wiring requirements.
The six structured cabling subsystems
1. Entrance Facilities (EF). Telecom facilities entering a building or residence from the outside — from a local service carrier or private network — pass through an opening in the exterior wall via a conduit. This cabling enters a room where other devices are deployed, including network connection points, patch panels, equipment racks, hardware connectors, power supplies and protection devices for grounding, shielding and lightning protection.
2. Equipment Room (ER). The area where entrance cabling connects to the internal building wiring infrastructure is the equipment room. It houses patch panels that provide connections for backbone cabling, horizontal cabling and intermediate cabling. As this room may also house network switches, PBXs, servers and other devices, it should be environmentally controlled to ensure that temperature and relative humidity levels are maintained according to equipment vendor specifications.
3. Backbone Cabling. Also called riser cabling — as it typically is installed in vertical channels, or risers, that connect to each floor — backbone cabling links EF, telecommunications and other ERs, and carrier spaces. Two subsystems have been defined for backbone cabling:
- Cabling Subsystem 2 is cabling between a horizontal cross-connect and an intermediate cross-connect (IC).
- Cabling Subsystem 3 is cabling between an IC and the main cross-connect (MC).
The cable types used in backbone cabling include the following:
- 100-ohm twisted-pair cabling: Cat3, Cat5e, Cat6 or Cat6a;
- multimode optical fiber cabling: 850 nanometer laser-optimized 50/125 micrometer (recommended); 62.5/125 μm and 50/125 μm (permitted); and
- single-mode optical fiber cabling.
Note: Entrance cables are usually determined by the carrier and are not the user’s responsibility.
4. Telecommunications Room (TR) and Telecommunications Enclosure (TE). This environmentally controlled area can be a dedicated room (TE) or part of another larger room (TR), such as a general utility room. Hardware in these spaces terminate horizontal and backbone cables. It’s also where local cables, called jumpers or patch cords, are used on patch panels to cross-connect different cables. ICs or MCs may be installed here as well to provide additional connection resources.
5. Horizontal Cabling (Cabling Subsystem 1). Getting telecom resources to users at their work areas or other rooms on a floor is the job of horizontal cabling. A typical cable run goes from the user’s device to the nearest TR on the same floor. The maximum allowed cable length between the TR and user device is 295 feet, regardless of cable type.
Horizontal cabling includes the cable, connectors, patch panels, jumpers and patch cords in the TR/TE. They may also include multiuser telecommunications outlet assemblies and consolidation points to connect multiple devices or cables in a single connector.
The cable types used in horizontal cabling include the following:
- four-pair 100-ohm unshielded or shielded twisted-pair cabling in Cat5e, Cat6 or Cat6a;
- multimode optical fiber cabling, two-fiber (also with a higher fiber count); and
- single-mode optical fiber cabling, two-fiber (also with a higher fiber count).
6. Work Area (WA). The area from a connector, or jack, in a wall outlet to a user device using a cable is considered the WA. It’s the final destination of a structured cable system.
Structured cabling has greatly simplified the process of installing voice and data communications equipment. Its continued use means new equipment, such as IoT systems, will be easily supported.