Demodulation

Discrete MultiTone

The alternative approach, called DMT (Discrete MultiTone), is illustrated in Fig. 2-28. In effect, what it does is divide the available 1.1 MHz spectrum on the local loop into 256 independent channels of 4312.5 Hz each. Channel 0 is used for POTS. Channels 1–5 are not used, to keep the voice signal and data signals [...]

{ 1 comment }

Ethernet

Both the Internet and ATM were designed for wide area networking. However, many companies, universities, and other organizations have large numbers of computers that must be connected. This need gave rise to the local area network. In this section we will say a little bit about the most popular LAN, Ethernet.The story starts out in [...]

{ 3 comments }

Internet Architecture

In this section we will attempt to give a brief overview of the Internet today. Due to the many mergers between telephone companies (telcos) and ISPs, the waters have become muddied and it is often hard to tell who is doing what. Consequently, this description will be of necessity somewhat simpler than reality. The big [...]

{ 0 comments }

THE OSI REFERENCE MODEL

The OSI network model (minus the physical medium) is shown in Fig. 1-20. This model is based on a proposal developed by the International Standards Organization (ISO) as a first step toward international standardization of the protocols used in the various layers (Day and Zimmermann, 1983). It was revised in 1995 (Day, 1995). The model [...]

{ 0 comments }

A Message is a Communication between the Client and Server

A service primitives is formally specified by a set of primitives (operations) available to a user process to access the service. These primitives tell the service to perform some action or report on an action taken by a peer entity. If the protocol stack is located in the operating system, as it often is, the [...]

{ 0 comments }

Operational Amplifier

Long before the advent of digital electronic technology, computers were built to electronically perform calculations by employing voltages and currents to represent numerical quantities. This was especially useful for the simulation of physical processes. A variable voltage, for instance, might represent velocity or force in a physical system. Through the use of resistive voltage dividers [...]

{ 1 comment }

Light Activated SCR

Like bipolar transistors, SCRs and TRIACs are also manufactured as light-sensitive devices, the action of impinging light replacing the function of triggering voltage. Optically-controlled SCRs are often known by the acronym LASCR, or Light Activated SCR. Its symbol, not surprisingly, looks like this: Optically-controlled TRIACs don’t receive the honor of having their own acronym, but [...]

{ 1 comment }

TRIAC

SCRs are unidirectional (one-way) current devices, making them useful for controlling DC only. If two SCRs are joined in back-to-back parallel fashion just like two Shockley diodes were joined together to form a DIAC, we have a new device known as the TRIAC: Because individual SCRs are more flexible to use in advanced control systems, [...]

{ 0 comments }

Common Collector Amplifier

Fig – Common Collector Amplifier : Our next transistor configuration to study is a bit simpler in terms of gain calculations. Called the common-collector configuration.It is called the common collector configuration because (ignoring the power supply battery) both the signal source and the load share the collector lead as a common connection point: It should [...]

{ 0 comments }

← Previous Entries