Community networking

The more effective deflvery of natural gas is being realized by the use of computerized operation centers that allow rapid responses to the variations ia gas demand. Automated valves, more precise measuting systems, and high speed communication networks make it possible to closely monitor and manage the transmission and deflvery of natural gas. This translates iato improved service and cost effectiveness. 

During the early 1970s, the necessary telecommunications technology became available with packet switching. ARPANet, the first operational packet-switched digital communications network, was implemented by the U.S. Department of Defense. Commercial systems (eg. Telenet, TYMNET, and GENet) became available shortiy thereafter. 

A laboratory information management system (LIMS) is a computer or computer network used to automate the acquisition and management of raw analytical data. In its simplest form, it tracks samples and test results through analytical laboratories and provides summaries of the status of these samples and tests. In its most advanced form, the system is interfaced to the laboratory s instmmentation and communication network to allow automation of data gathering, compilation, and reporting. 

The Contraceptive diaphragm, Emory University, School of Medicine, Healthcare Communications Network, New York, 1989. 

Microprocessor technology permitted these technical issues to be addressed in a cost-effec tive manner. In the mid-1970s, a process control architecture referred to as a distributed control system (DCS) was introduced and almost instantly became a commercial success. A DCS consists of some number of microprocessor-based nodes that are interconnec ted by a digital communications network, often called a data highway. The key features of this architecture are as follows ... 

As the data within the DCS are digital in nature, interfaces to upper level computers are technically easier to implement. Unfortunately, the proprietary nature of the communications networks within commercial DCS products complicate the implementation of such interfaces. Truly open DCS architectures, at least as the term open is used in the mainstream of computing, are not yet available. 

Noise and resonance problems (Section 23.5.2(C)) in the electrical distribution and communication networks. 

Generally, a few harmonic quantities are always present in an a.c. system, as normally some non-linear loads always constitute a power system. These harmonics may not affect the operation of the inductive loads connected on the system as much as a capacitive load or a communication network that may be running in parallel or in the vicinity of such a power system. 

But as the harmonics do exist in the system, they do affect an inductive load. They may also disturb a communications network as a result of capacitive coupling, whose effects are magnified in the presence of capacitor units in the power system. It is therefore considered relevant to discuss this subject in more detail to make the harmonic study more informative. 

It is desirable to contain the harmonic effects as far as practicable to protect the capacitors as well as inductive loads connected on the system and the communication network, if running in the vicinity. 

Use of screened cables in the communication network and grounding the screen effectively. Metallic-sheath or armoured cables are not recommended. 

To block carrier frequencies to travel beyond the communication network and weaken the vital signals. 

To drain out the excessive voltages transferred to the communication network through the CVT, caused by lightning, switching or a fault. 

Isolated neutral In i symmetrical ihree-phtise three-wire star-connected system the summation of all phase quantities, voltage or cunent will be zero, as illustrated in Figure 21.7. When a few harmonics exist in such a system, this balance is disturbed and the sum of these quantities is not zero. The third harmonic quantities can find their outlet only through t neulral of the system. Since there is no neutral available in this system, no third harmonic quantities will tlow into or out of the supply system and affect the equipment associated with it or a communication network if existing in the vicinity (Figure 23.12(a)). 

Grounded neutral When the neutral is grounded, the third harmonic quantities will be able to find their w ay through it. This system can thus be considered to contain the third harmonic quantities and will affect operation of the equipment connected on it and communication networks if existina in the vicinitv (Figure 23.12(c)),... 

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

Intelligent transmitters have two major components (1) a sensor module which comprises the process connections and sensor assembly, and (2) a two-compartment electronics housing with a terminal block and an electronics module that contains signal conditioning circuits and a microprocessor. Figure 6.9 illustrates how the primary output signal is compensated for errors caused in pressure-sensor temperature. An internal sensor measures the temperature of the pressure sensor. This measurement is fed into the microprocessor where the primary measurement signal is appropriately corrected. This temperature measurement is also transmitted to receivers over the communications network. 

FIGURE 14.44 Class fibers, such as this one, about the diameter of a human hair, are used in communication networks when large amounts of information must be transmitted in a short time. 

Mankind As above plus e, hv, sound Vast communication network Control of the environment... 

The necessary communication network in all chemotypes was based originally on exchangeable reduced available internal ions such as Mg2+ and Fe2+ and reduced organic chemicals, substrates and coenzymes, often linked to phosphate, and feedback and forth of information about cell conditions to and from the genetic central control. 

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