Data communication

Data Communication Wires. Electronic cables such as data communication wires employ three basic designs coaxial, twisted pair, and fiber optics (3,4) (Eig. 1). Coaxial cables are so named because the axis of curvature of its outer conductor is concentric to its inner central wire. The metal braiding wrapped around the insulated center wire acts as the return current conductor in addition to shielding the wire from various interferences. 

The twists of twisted pair cable act as a shield against radio frequency interference (REI), and electromagnetic interference (EMI), and against the cross talk interference that a wire exerts on nearby wires the more twist the less interference. Telephone wires can use large numbers of pairs. In most cases the pairs are not shielded with braiding or foil, as shown in Eigure lb for data communication wire. Data communication wires work at very high... 

Pigure 10 shows the typical commercial performance of LEDs used for optical data communication. Both free-space emission and fiber-coupled devices are shown, the latter exhibiting speeds of <10 ns. Typically there exists a tradeoff between speed and power in these devices, however performance has been plotted as a function of wavelength for purposes of clarity. In communication systems, photodetectors (qv) are employed as receivers rather than the human eye, making radiometric power emitted by the devices, or coupled into an optical fiber, an important figure of merit. 

The relevance of photonics technology is best measured by its omnipresence. Semiconductor lasers, for example, are found in compact disk players, CD-ROM drives, and bar code scaimers, as well as in data communication systems such as telephone systems. Compound semiconductor-based LEDs utilized in multicolor displays, automobile indicators, and most recendy in traffic lights represent an even bigger market, with approximately 1 biUion in aimual sales. The trend to faster and smaller systems with lower power requirements and lower loss has led toward the development of optical communication and computing systems and thus rapid technological advancement in photonics systems is expected for the future. In this section, compound semiconductor photonics technology is reviewed with a focus on three primary photonic devices LEDs, laser diodes, and detectors. Overviews of other important compound semiconductor-based photonic devices can be found in References 75—78. 

Held, G. (1999). Data Communications Networking Devices, 4th ed. New York John Wiley Sons. 

A recent data communications protocol for Building Automation and Control Networks (BACnet), ASHRAE Standard 135-1995, is an important step to ensure that controllers made by different manufacturers can communicate with each other in a simple way, avoiding the expense of additional interface hardware and communication software. 

The telephone is still one of the primary means of communication for clinical trial personnel. The telephone is used for both voice and digital communications. Voice communication is the normal person-to-person telephone call. Data communication with the telephone is the transmission of digital data from one location to another. Various software packages have been developed for this purpose. Using a voice modem connected to a telephone, a user on a local computer can connect to another remote computer that has a modem connected to a telephone and download or upload data files. Local and remote users can also communicate with text messages. The local computer operator can even control the remote computer for trouble-shooting or system update. 

File transfer protocol (FTP) technology is a data communication tool that allows sending, accessing, and sharing files quickly and easily through a secure environment. The user logs onto the FTP site with a valid account name and a valid password. This method allows participants to share data files instantly. 

The type of system chosen determines the types of hardware and software needed. It also determines the processes for acquiring the necessary hardware and software. The hardware selection may include desktops, laptops, printers, scanners, fax machines, and storage devices, and the software selection includes the system development software, the database management software, the data communication software, the data conversion software, specialized proprietary software, servers, and hrewalls. 

Pulse Code Formats for Fiber Optical Data Communication Basic Principles and Applications, David J. Morris... 

In this section, those devices necessary for communication and integration of industrial chemical processing operations, such as electronic controllers, two-way radios, and wireless data communications are discussed. Typically, SCADA systems would also be discussed in this section however, SCADA was discussed in detail in chapter 7. 

Wireless data communications devices are used to enable transmission of data between computer systems and/or between a SCADA server and its sensing devices, without individual components being physically linked together via wires or cables. In industrial chemical processing systems, these devices are often used to link remote monitoring stations (i.e., SCADA components) or portable computers (i.e., laptops) to computer networks without using physical wiring connections. 

Wireless radios broadcast these voice or data communications over the airwaves from the transmitter to the receiver. While this can be an advantage in that the signal emanates in all directions and does not need a direct physical connection to be received at the receiver, it can also make the communications vulnerable to being blocked, intercepted, or otherwise altered. However, security features are available to ensure that the communications are not tampered with. 

WAP. The WAP provides the wireless data communication service. It usually consists of a housing (which is constructed from plastic or metal depending on the environment it will be used in) containing a circuit board, flash memory that holds software, one of two external ports to connect to existing wired networks, a wireless radio transmitter/receiver, and one or more antenna connections. Typically, the WAP requires a one-time user configuration to allow the device to interact with the local area network (LAN). This configuration is usually done via a Web-driven software application which is accessed via a computer. 

Two of the primary applications for wireless data communications systems are to enable mobile or remote connections to a LAN, and to establish wireless communications links between SCADA remote telemetry units (RTUs) and sensors in the field. Wireless card connections are usually used for LAN access from mobile computers. Wireless cards can also be incorporated into RTUs to allow them to communicate with sensing devices that are located remotely. 

From the general audience came this comment "Instruments today are not too compatible to transfer information. There is the RS-232 port with its 8-bit code and all sorts of hand shaking and lines to be hooked up properly. It is just difficult to set up. And as we have already said in this panel discussion, "There are not adequate conventions for data communication and transportability. I think that the answer to that is that the analytical chemist and these people who are interested in that sort of data exchange will have to become extremely active in this area to reflect the needs of the user. ... 

Currently, KARMA is in the prototyping phase. Although the hardware is connected via the high bandwidth network, it is necessary to implement the servers for data communications. Additionally, a completely new graphics package is in development for karma. The next two steps in terms of development are the turnkey and production versions of karma. 

Gariiy data communication in the input-output interfaces between user and model. 

Overall, most of the requirements for a process spectrometer/analyzer are straightforward to implement, but they do require attention at the design level. Another important area, which is FTIR specific, is the user interface and the need to provide for industry standard data communications. Standard software packages do exist for process instrumentation. For prototype development, and even for the front-end interface in a stand-alone mode of operation, software products, such as National Instraments Lab View and the Mathworks MatLab, are also important instrumentation development tools. Note that National Instruments also provides important computer-based electronics and hardware that meet most of the computer interfacing, and system control and communications needs for modem instrumentation. For practical installations, a product known... 

For the water analysis, automation is clearly best achieved with an auto-injector for the mechanical handhng of the samples coupled with on-hne data capture, using the computer to analyse the peak data. Serious consideration was given to employing the very considerable in house automation experience to construct a purpose-built auto-injector. However, in the interests of a speedy implementation of the automatic system, it was decided to purchase a commercially available auto-injector and to concentrate the laboratory s efforts on the area of on-hne data capture. Interfacing the complete system assembly via a data communications network required the development of a special control device (commhox), which allowed the LGC hardware to run unattended hut provided an audible warning in event of a fault condition. 

With suitable scan-line delay circuits, the filter may be applied in real time to live video images. In data communications, bandwidth extrapolation offers the opportunity to make far better use of channel capacity than is now possible. The bounded methods produce their most impressive restorations when o(x) spends a lot of time at or near the bounds. The present method was designed for use with both upper and lower bounds, which makes it ideal for the bilevel signals used in digital transmission. 

Operating system software—document version and data communication protocols, and establish extent of use. 

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