What is WAN ?

A wide area network (WAN) is a network that covers a broad area (i.e., any telecommunications network that links across metropolitan, regional, or national boundaries) using private or public network transports. Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location. The Internet can be considered a WAN as well, and is used by businesses, governments, organizations, and individuals for almost any purpose imaginable


Related terms for other types of networks are personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs) which are usually limited to a room, building, campus or specific metropolitan area (e.g., a city) respectively.
http://upload.wikimedia.org/wikipedia/commons/thumb/6/6e/LAN_WAN_scheme.svg/300px-LAN

WAN is a computer network spanning regions, countries, or even the world. However, in terms of the application of computer networking protocols and concepts, it may be best to view WANs as computer networking technologies used to transmit data over long distances, and between different LANs, MANs and other localised computer networking architectures. This distinction stems from the fact that common LAN technologies operating at Layer 1/2 (such as the forms of Ethernet or Wifi) are often geared towards physically localised networks, and thus cannot transmit data over tens, hundreds or even thousands of miles or kilometres.

What is RS 232

This article is about the RS-232 standard. For RS-232 variants, see serial port.

"V.24" redirects here. For other uses, see V24 (disambiguation).

A DB-25 connector as described in the RS-232 standard

In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between DTE (data terminal equipment) and DCE (data circuit-terminating equipment, originally defined as data communication equipment^[1]). It is commonly used in computer serial ports. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997.

An RS-232 serial port was once a standard feature of a personal computer, used for connections to modems, printers, mice, data storage,uninterruptible power supplies, and other peripheral devices. However, the low transmission speed, large voltage swing, and large standard connectors motivated development of the Universal Serial Bus, which has displaced RS-232 from most of its peripheral interface roles. Many modern personal computers have no RS-232 ports and must use either an external USB-to-RS-232 converter or an internal expansion card with one or more serial ports to connect to RS-232 peripherals. RS-232 devices are still found, especially in industrial machines, networking equipment, and scientific instruments.

GPS Time Synchronization

GPS or Global Positioning System is a navigation aid system which uses signals from satellites to calculate the actual position of a GPS capable receiver. The GPS satellites are part of the military navigation system of the US Army, but they also transmit navigation signals on public frequencies which are free to use by everyone.

GPS satellites (and now other global navigation systems) include three or four atomic clocks that are monitored and controlled to be highly synchronized and traceable to national and international standards (known as UTC). So for time synchronization, the GPS signal is received, processed by a local master clock, time server, or primary reference, and passed on to "slaves" and other devices, systems, or networks so their "local clocks" are likewise synchronized to UTC.

The GPS system allows a maximum of 32 satellites around the earth which each transmit their own position and time on a regular interval to the earth. A GPS receiver will receive these signals and use geometric calculations to estimate the location of the receiver relative to those satellites. This GPSsignal can not only be used to calculate a position, but it can also be used as a very accurate time base.  Typical accuracies range from better than 500 nanoseconds to a few milliseconds depending on the synchronization protocol. It is the process of synchronization to GPS that can provide atomic clock accuracy without the need for a local atomic clock.

GPS clock synchronization eliminates the need for manual clock setting (an error-prone process) to establish traceability to national and international standards so various events can be correlated even when they are time-stamped by different clocks. The benefits are numerous and include: legally validated time stamps, regulatory compliance, secure networking, and operational efficiency. 

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