Cable and Plugs, a Timeline from 1873 plus Ethernet in 1973 and Novell in 1980
Connections and Connectors by Quayle Consulting & Swiss company Stromasys
that includes a DEC Wiring Connectors Cable Page
The RS-232 standard specifies this as 15 metres (50 feet).
However this is a conservative figure accounting for high serial speeds over high capacitance cabling, for example using a baud rate of 9600 (a common console speed) over typical Cat 5 cabling, the maximum length increases to 100 - 150 meters (328 - 500 feet).
After the 1960s the standard telephone service connector in Australia was the 600 series plug which has up to three flat pins plus a non-conducting spigot, which ensures correctly oriented insertion. Each pin carries up to two conductors by means of two contacts, one on each side of the pin. The pin bodies are of a non-conductive plastic material.
Each RJ45 connector has eight pins, which means an RJ45 cable contains eight separate wires. If you look closely at the end of an Ethernet cable, you can actually see the eight wires, which are each a different color. Four of them are solid colors, while the other four are striped.
Quora question on Ethernet (designed in 1973) Jan Peterson, works at Forcepoint Answered March 13, 2020 Does Ethernet communicate in a serial way or in a parallel way Originally Answered: Is Ethernet communication serial or parallel? Old Ethernet was a completely serial medium, but modern "fast" Ethernet can send data in both directions at the same time so it is somewhat parallel. Over fiber-optic cable, multiple light frequencies (colors) can be used to add further parallelism. Traditional Ethernet is a serial communications medium. Think for a minute about what Ethernet actually is... what is actually happening. A small radio is generating RF energy and sending it down the wire. The signal is modulated (just like any radio signal) and the information is carried by that modulation. If you go back to the early days of Ethernet (it was invented in the 1970s) you will remember that we used a single Ethernet cable for a specific network. This was a RG-8 cable (similar to your cable TV cable). With so-called "thick" Ethernet cable, the cable was marked at intervals of about 2.5 meters and at each of these marks you could install a "transceiver" (a small radio transmitter/receiver). This could be done by cutting the cable, installing N-type connectors on the cable ends, and connecting the cable ends directly to the transceiver, or, more typically, using a "vampire tap" where a small hole was drilled into the cable and the transceiver was clamped over this hole with a small wire going into the cable and touching the center conductor. The transceiver was typically connected to the computer through an AUI cable, which was a 15 conductor cable that attached to an AI port on the board in the computer. These AUI cables had a very distinctive connector that had a sliding clamp to hold it in place. The board would generate signals which were sent down the AUI cable to the transceiver, where they were converted into radio frequency energy and dumped into the cable. Further along the cable, other transceivers would receive the radio signal, convert it back to an electrical signal, and deliver it to the board in the computer. Later, a "thin" version of Ethernet was developed using standard RG-58 coax cable and the ubiquitous "T" connectors that would be used to connect the transceiver (typically directly on the board in the computer, but occasionally a separate transceiver connected via AUI cable as above) to the cable. A "terminator" was used at either end of the cable to dampen the radio signal and prevent it from reflecting back and forth across the length of the cable, disrupting the network. Typically, when you had problems with this type of network, it was because someone disconnected the cable from the T connector instead of disconnecting the T connector from their computer when they needed to move it around. Eventually, Ethernet over twisted pair wire came into use. These still use RF energy along the cable. Due to the nature of twisted pair signaling, it is possible to send different signals in both directions at the same time (known as "full duplex"). With the advent of switches, that isolated each connected station to its own private physical network, and switches that had some amount of data storage capability in their backplanes, there is some amount of parallelism possible. In addition, there are protocols for sending Ethernet-type signals over fiber-optic cables and some types of fiber-optic cabling can support multiple frequencies on the cable at the same time, allowing further parallelization.
Novell based its network protocol on Xerox Network Systems (XNS), and created its own standards which it named Internetwork Packet Exchange (IPX) and Sequenced Packet Exchange (SPX). These protocols were based on a client-server model. File and print services ran on the NetWare Core Protocol (NCP) over IPX, as did Routing Information Protocol (RIP) and Service Advertising Protocol (SAP). All of these NetWare protocols mapped to various layers of the OSI model. Novell did extremely well throughout the 1980s. It aggressively expanded its market share by selling its expensive Ethernet cards at cost. As author James Causey would later write, "NetWare deserves the lion's share of the credit for elevating PC-based local area networks from being cute toys to providing powerful, reliable, and serious network services. NetWare was the first Intel-based network operating system to provide a serious alternative to mainframe-based server networks, providing critical reliability and security features needed in the modern enterprise." Novell acquired Kanwal Rekhi's company Excelan in 1989; Excelan manufactured smart Ethernet cards and commercialized the Internet protocol TCP/IP, solidifying Novell's presence in these areas. The acquisition combined Novell's $281 million in annual revenue with Excelan's $66 million. Rekhi became a high-ranking Novell executive, and played an influential strategic and managerial role with the company over the next several years. Excelan was based in San Jose, California, and they, along with a couple of prior Novell acquisitions, formed the basis for Novell's presence in Silicon Valley going forward. A key software introduction came in 1989 with the release of NetWare 386, also known as NetWare 3.0, which gave NetWare more modern architectural qualities, in conjunction with new capabilities in the Intel 386 processor. NetWare 3 supported interactions with Apple's Macintosh computers as well as with Unix-based workstations. From 1988 to 1992, Novell's revenues rose almost three-fold, to $933 million a year, with about half of Novell's sales coming from North America and half from overseas. At its high point around 1993, NetWare had a roughly two-thirds share of the market for network operating systems. The inclusion of networking as a core system component in all mainstream PC operating systems after 1995 led to a steep decline in Novell's market share. Unlike Windows 3.1 and its predecessors, Windows NT, Windows 95, Linux, and OS/2 all included network functionality which greatly reduced demand for third-party products in this segment. In 1996, the company began a move into Internet-enabled products, replacing reliance on the proprietary IPX protocol in favor of a native TCP/IP stack. Support for the new Java programming language also began to be added to NetWare. By 1999, Novell had lost its dominant market position, and was continually being out-marketed by Microsoft as resellers dropped NetWare, allowing Microsoft to gain access to corporate data centers by bypassing technical staff and selling directly to corporate executives. In November 2003, Novell acquired Linux OS developer SuSE, which led to a major shift of power in Linux distributions. IBM also invested US$50 million to show support of the SuSE acquisition. Novell announced in November 2010 that it had agreed to be acquired by The Attachmate Group for US$2.2 billion, and planned to operate Novell as two units, one being SUSE. As part of the deal, 882 patents owned by Novell were sold to CPTN Holdings LLC, a consortium of companies led by Microsoft and including Apple, EMC, and Oracle. In September 2014, mainframe software company Micro Focus announced it was buying The Attachmate Group, including Novell, for US$1.2 billion. The SUSE organization was split out separately from the rest of the former Novell organization within Micro Focus. The Novell products themselves were relabeled and dispersed among the file and networking services, collaborations, and security product lines of Micro Focus, such that offerings like Open Enterprise Server, GroupWise, and Zenworks became billed as Micro Focus products with no mention of their Novell past.
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