Communications wiring standards are defined by a number of national and international agencies, including the Electrical Industries Association (EIA), the Telecommunications Industry Association (TIA), the Institute of Electrical and Electronics Engineers (IEEE) and the National Electrical Manufacturer's Association (NEMA). These committees recognize and develop definitions for multiple electrical and communications definitions, i.e., how things operate, how devices will inter-connect, how signals will be formatted, and how manufacturers can design and construct equipment so as to ensure compatibility within the marketplace.
The process of setting national and international standards is time-consuming as it involves a committee and meeting structure, often on an international basis, and may take several years to get draft standards distributed for comment. Such a draft standard is voted on by the members of the various organizations and, upon concurrence, testing and announcement follows before an end-user may be assured that their equipment or wiring standards will be in conformance with a national or international standard. In the United States, the final standard is issued and maintained by the American National Standards Institute (ANSI).
Large manufacturers within the communications industry, such as IBM or DEC, often create a de facto standard by virtue of their dominance of a particular field. For example, IBM's dominance of the early years of token-ring development paralleled the introduction of the IBM wiring standard and its reliance upon shielded twisted pair for data communications.
Seven Levels/Grades Media
Since Winter of 1990, electrical manufacturing associations have redefined existing wiring product lines and introduced new cables according to a generally agreed-upon set of "levels" or "grades" of media. For the purposes of this paper, these levels are defined as follows:
It may be helpful to understand that Category 3 is the appropriate definition for the recent 10BaseT (Ethernet over unshielded twisted pair) standard, while Category 5 is the targeted range for the Fiber Distributed Data Interface (FDDI) over copper standard, or CDDI (Copper Distributed Data Interface) now under development.
It is noted that, as a result of the adoption of national wiring standards, major manufacturers and distributors of wiring projects (e.g. Anixter, Belden, etc.) have developed marketing efforts for their products which define wiring performance "Levels" or similar indexes. Much of these "Levels" parallel work by the EIA/TIA defined as "Category," but in fact project standards which do not yet exist. This results in considerable confusion as to what is actually a standard and which materials are conforming. A vendor product specification is only relevant if a standard has been specifically adopted and published by the EIA/TIA committee process.
Shielded versus Unshielded ("THE debate")Throughout this document are references to shielded versus unshielded twisted pair cables. By way of background, shielded cable was developed to provide protection for data signals from electrical interference generated by power cables, fluorescent lighting, and other data signals. At an earlier point in communications wiring history, it was a basic requirement for maintaining data speeds as low as 9600 bits per second. Driven by the enormous existing base of unshielded telephone cables present in buildings, manufacturers developed devices to balance or re-balance the signal characteristics over twisted pair cabling. In time, techniques and standards defining the size, purity, and twists in twisted pair cabling were developed to take advantage of both existing unshielded cables, and the relatively lower costs of placing new unshielded cabling versus new shielded or coax cable.
The large-scale introduction of network hardware and software produced intelligent hubs that provided sophisticated pre-balancing and re-balancing, and restoration of signals carried over unshielded twisted pair cables. As a result, national standards now define a ten megabits per second standard for Ethernet over unshielded twisted pair (UTP) and a new 16 megabits per second standard for token-ring over UTP. As indicated above, discussions are underway on signal processing required to carry the 100 megabits per second speeds of Fiber Distributed Data Interface (FDDI) over copper cables (CDDI).
Industry leaders speaking about future wiring talk about a combination of unshielded
twisted pairs and fiber strands. Because of the developments in signal
There have been three distinct stages in the integration of voice and data wiring at UCSB. The first stage of wiring was distinctly telephone wiring, with the telephone companies providing, maintaining, and enforcing standards in phone wiring. The telephone companies did provide limited data services over their cable, but did so only as an adaptation of their voice wiring standard. In the early development of data terminal attachments, computer shops ran their own cables (coaxial, shielded, and unshielded), according to their own system requirements.
During the first campus wiring stage, Communications Services pulled a package of separate data, voice, and video cables to work stations in all new and re-modeled campus areas. These cables did terminate in a common wall plate, but followed individual distribution routes within terminal facilities. Existing cable packages placed in the years 1982-1987 will not meet the specification for local area network wiring defined in the 10BaseT standard.
The second stage of joint wiring was partially developed by "pirating" of telephone cables by and for data users when it was available. Upon de-regulation of telephone services, increased usage of telephone cabling for data took place. Under a common utility, Communications Services, most ASCII, and later System Network Attachment (SNA) attachments, took place over telephone cables, often sharing larger cables with telephone services.
Early telephone multiple pair cables (campus pre-1975) were not twisted pair cables and may, as a result, be unsatisfactory for data transmission as part of a local area network. Multiple pair telephone cables placed after 1987 and prior to 1989 should be tested for use in a 10BaseT local area network according to the EIA/TIA-568 specification (see Appendix A-1).
The third stage of voice-data wiring integration occurred on this campus with the adoption of the IBM Type 2 single sheath cable standard by Communications Services in late 1985. The IBM-Type 2 standard specifically defines shielded and unshielded wire within a single sheath for data and voice wiring. Composite cables containing both fiber and multiple twisted pair could result in an economically viable "single cable" technology carrying all communications.
In the period following the adoption of the initial Campus Wiring Standard, two patterns of voice-data wiring integration have occurred specifically in the riser cabling:
The second pattern now reflects the campus standards practice. Both Category 3 and Category 5 cables are placed in the risers.