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 2 or 3 dots and dashes  per second, computers now communicate at speeds of over 1 Gigabit, 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 6a and Cat 7a standards, and more   information  on these can be found in the Network Cabling Help eBook. 

Numbers and Dates

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

The History of Network Cabling