The History of Data Cabling

The Beginning
We tend to think of digital communication as a new idea but in 1844 a man called Samuel Morse sent a message 37 miles from Washington D.C. to Baltimore, using his new invention �The Telegraph�. This may seem a far cry from today's computer networks but the principals remain the same.

Morse code is type of binary system which uses dots and dashes in different sequences to represent letters and numbers, modern data networks use 1�s and 0�s to achieve the same result. The big difference is, that while the telegraph operators of the mid 19th Century could perhaps transmit 4 or 5 dots and dashes per second, computers now communicate at speeds of up to 1 Giga bit, or to put it another way, 1,000,000,000 separate 1�s and 0�s every second.

Not long after Morse's Telegraph, a French inventor called Emile Baudot developed a printing telegraph machine which used a typewriter style keyboard, this allowed virtually anyone to send and receive telegraph messages. Baudot used a different type of code for his system because Morse code didn't lend itself to automation, this was due to the uneven length and size of bits required for each letter. Baudot used a five bit code to represent each character, this would normally only give 32 possible combinations (00000 to 11111 = 32).

It clearly wasn't enough for 26 letters and 10 digits but he got around this problem by using two 'shift characters' for figures and letters, which performed the same sort of function as a typewriter shift key. Now he had 62 combinations for letters, figures and punctuation marks. To this day, the speed of serial communications is still measured in Baud rate, after Emile Baudot.

Improvements were made to Baudot's machine by an English inventor called Donald Murray. Murray sold the rights for his machine to Western Union who gradually replaced all of its Morse telegraphs with the new 'teletypewriters'.

Despite its long running success, the Baudot five bit code could only use 'upper case', so it had to be replaced with something that would allow more alphanumeric characters to be used. In 1966, a group of American communications companies got together to devise a new code, this time they used 7 bits which could represent 128 characters. This is known as the American Standard Code for Information Interchange or the ASCII code. It was immediately accepted by nearly all of the worlds computer and communications companies, except of course IBM, who decided to make their own standard.

IBM's version is the Extended Binary Coded Decimal Interchange Code or EBCDIC, it uses 8 bits and can represent 256 characters, but apart from using it in their mid range and mainframe computers, it never really caught on. Not to be completely out done, IBM adopted the ASCII code but extended it by using an eighth bit so it could represent 256 characters, they called it 'Extended ASCII'.

Although the telegraph and the teletypewriter were the forerunners of data communications, it has only been in the last 30 years that things have really started to speed up. This was born out of necessity, as the need to communicate between computers at ever increasing speeds, has driven the development of faster and faster networking equipment and, higher and higher specification cables and connecting hardware.

Development of new network technology
Ethernet was developed in the mid 1970's by the Xerox Corporation at their Palo Alto Research Centre (PARC) in California, and in 1979 DEC and Intel joined forces with Xerox to standardize the Ethernet system for everyone to use. The first specification by the three companies called the 'Ethernet Blue Book' was released in 1980, it was also known as the 'DIX standard' after their initials. It was a 10 Mega bits per second system (10Mbps, = 10 million 1's and 0's per second) and used a large coaxial backbone cable running throughout the building, with smaller coax cables tapped off at 2.5m intervals to connect to the workstations. The large coax which was usually yellow became known as 'Thick Ethernet' or 10Base5, the '10' refers to the speed (10Mbps), the 'Base' because it is a base band system (base band uses all of its bandwidth for each transmission, as opposed to broad band which splits the bandwidth into separate channels to use concurrently), and the '5' is short for the systems maximum cable length, in this case 500m.

The Institute of Electrical and Electronic Engineers (IEEE) released the official Ethernet standard in 1983 called the IEEE 802.3 after the name of the working group responsible for its development, and in 1985 version 2 (IEEE 802.3a) was released. This second version is commonly known as 'Thin Ethernet' or 10Base2, in this case the maximum length is 185m even though the '2' suggest that it should be 200m.

In 1984, IBM introduced Token Ring which was able to transmit data at 4Mbps, this system uses a thick black 2 pair shielded cable with large 4 pole connectors. The IBM data connector, or IDC as it is sometimes called, was an engineering masterpiece. Instead of the normal plug and socket arrangement of male and female gendered connectors, the Data Connector was designed to mate with itself, a sort of hermaphrodite. Although the IBM Cabling System is to this day a very high quality and robust data communication media, it has lost favour with a lot of customers. This is partly due to its large size and cost, and partly because it only has 4 cores and therefore is not as versatile as an 8 core UTP.

It is rumoured that Type 1 cable was originally tested to 300MHz even though it was only categorized as a 20MHz cable for Token Ring, and the newer version, Type 1A was reportedly tested to 600MHz and categorized as a 100MHz cable.
There were many other types of network at that time (too numerous to mention here), which used different types of cables and connectors, so it soon became clear that a standard for telecommunications wiring was needed.

In 1985, the Computer Communications Industry Association (CCIA) asked the Electronic Industries Association (EIA) to develop a cabling standard which would define a generic telecommunications wiring system for commercial buildings, that will support a multi product, multi vendor environment. In essence this would be a cabling system which would run all current and future networking systems over a common topology using a common media and common connectors.

By 1987 several manufacturers had developed Ethernet equipment which could utilize twisted pair telephone cable, and in 1990 the IEEE released the 802.3I Ethernet standard 10BaseT (the 'T' refers to Twisted pair cable). In 1991 the EIA together with the Telecommunications Industry Association (TIA) eventually published the first telecommunications cabling standard called EIA/TIA 568, the structured cabling system was born. It was based on Category 3 Unshielded Twisted Pair cable (UTP), and was closely followed one month later by a Technical Systems Bulletin (TSB-36) which specified higher grades of UTP cable, Category 4 and 5 (Cat 4 & Cat 5).
Cat 4 specified data rates of up to 20MHz and Cat 5 up to 100MHz which at the time must have seemed like ample bandwidth for future development, but now, less than ten years later, even Cat 5 is being pushed to its limits by new networking technologies.

Recent developments have been Cat 5e, Cat 6 and Cat 7 standards, and more information on these can be found on the Questions and Opinions page.

Numbers and Dates
If you like number and dates, here are some of the more important ones in the history of data communications.

1844 - May 24th - The Telegraph invented by Samuel Morse.
1845 - English patent for a telegraph by William Cooke and Charles Wheatstone.
1846 - A man called Royal House invented a printing telegraph which required two operators at each end.
1851 - Western Union Company was formed by the merger of 12 telegraph companies.
1861 - German inventor Phillip Reis invented a device for transmitting musical tones called a 'Telephone'.
1874 - Jean-Maurice-Emile Baudot patented the Baudot telegraph code.
1876 - February 14th - Alexander Graham Bell filed a patent for the Telephone.
1876 - February 14th - A few hours after Bell, Elisha Gray filed a patent for the Telephone.
1889 - Almon Brown Strowger invented the 'Dial Telephone' and 'Strowger Switch'.
1948 - Bell Labs invented the transistor.
1966 - ASCII code was devised.
1969 - RS232 serial standard was established.
1976 - Paper on Ethernet was published by Bob Metcalfe and David Boggs at PARC.
1979 - DEC and Intel join forces with Xerox to develop Ethernet.
1980 - DEC, Intel and Xerox publish the 'Ethernet Blue Book' or DIX standard.
1983 - IEEE 802.3 Ethernet standard.
1984 - IBM introduce 4Mbps Token Ring.
1985 - IEEE 802.3a Thin Ethernet standard, 10Base2.
1985 - IEEE 802.3b Ethernet standard 10Broad36, 10Mbps using broad band.
1987 - IEEE 802.3d Fibre Optic Inter-Repeater Link (FOIRL) & IEEE 802.3e 1Mbps Ethernet over twisted pair.
1990 - IEEE 802.3i Ethernet standard, 10BaseT.
1991 - July - EIA/TIA 568 standard for telecommunications wiring in commercial buildings.
1991 - August - EIA/TIA TSB 36 for higher grade cables (Cat 4 and Cat 5).
1992 - August - EIA/TIA TSB 40 for higher grade connecting hardware.
1993 - IEEE 802.3j Ethernet standard 10BaseFL, Ethernet fibre links up to 2km.
1994 - January - EIA/TIA TSB 40A - included patch cords and testing in more detail.
1994 - January - EIA/TIA 568 revised to EIA/TIA 568A and included TSB 36, TSB 40A and other amendments.
1995 - IEEE 802.3u Fast Ethernet standards 100BaseTX (2 pair Cat 5), 100BaseT4 (4 pair Cat 3), 100BaseFX.
1997 - IEEE 802.3x Full duplex Ethernet standard.
1997 - IEEE 802.3y 100BaseT2 Fast Ethernet standard (2 pair Cat 3).