That is why there is a shift towards digital transmission despite large analog base. Some of the advantages of digital transmission are highlighted below: ; Analog circuits require amplifiers, and each amplifier adds distortion and noise to the signal. In contrast, digital amplifiers regenerate an exact signal, eliminating cumulative errors. An incoming (analog) signal is sampled, its value is determined, and the node then generates a new signal from the bit value; the incoming signal is discarded. With analog circuits, intermediate nodes amplify the incoming signal, noise and all.

Voice, data, video, etc. Can all by carried by digital circuits. What about carrying digital signals over analog circuit? The modem example shows the difficulties in carrying digital over analog. A simple encoding method is to use constant voltage levels for a "1 " and a Can dead to long periods where the voltage does not change. Easier to multiplex large channel capacities with digital. Easy to apply encryption to digital data. Better integration if all signals are in one form. Can integrate voice, video and digital data.

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Depending on some type of typical signal formats or modulation schemes, a few terminologies evolved to classify different types of signals. So, we can have either a base band or broadband signaling. Base-band is defined as one that uses digital signaling, which is inserted in the transmission channel as voltage pulses. On the there hand, broadband systems are those, which use analog signaling to transmit information using a carrier of high frequency. In baseman Lana, the entire frequency spectrum of the medium is utilized for transmission and hence the frequency division multiplexing (discussed later) cannot be used.

Signals inserted at a point propagates in both the directions, hence transmission is bi-directional. Baseman systems extend only to limited distances because at higher frequency, the attenuation of the signal is most pronounced and the pulses blur out, causing the large distance communication totally impractical. Since broadband systems use analog signaling, frequency division multiplexing is possible, where the frequency spectrum of the cable is divided into several sections of bandwidth. These separate channels can support different types of signals of various frequency ranges to travel at the same instance.

Unlike base-band, broadband is a unidirectional medium where the signal inserted into the media propagates in only one direction. Two data paths are required, which are connected at a point in the network called headed. All the stations transmit towards the headed on one path and the signals received at he headed are propagated through the second path. Fill In the blanks: (a) A signal is a Electromagnetic or coding of data. (b) The four parameters that are used to characterize a signal in time domain concept are amplitude, and . C) With the help of we can find out the different frequency components of a signal, and these components are visualized with the help of gives a measure of the span of the spectral components of a signal. (e) The noise created by the agitation of electrons of the transmission channel is termed as by bunching several cables together is known as Short Answers Questions: (f) The noise created Q-1 . Distinguish between data and signal. Mans: Data is an entity, which conveys some meaning. On the other hand, the signal is a representation of data in some electric, electromagnetic or optical form.

So, whenever data needs to be sent, it has to be converted into signal of some form for transmission over a suitable medium. Q-2. What do you mean by a "Periodic Signal"? And what are the three parameters that characterize it? Mans: A signal is periodic signal if it completes a pattern within a measurable timeshare. A periodic signal is characterized by the following three parameters. Amplitude: It is the value of the the time period, I. E. F=1/T. The unit of frequency is Hertz (Hazy) or cycles per second.

Phase: It gives a measure of the relative position in time of two signals within a single period Q-3. Distinguish between time domain and frequency domain representation of a signal. Mans: Whenever a signal is represented as a function of time, it is called time domain representation. An electromagnetic signal can be either continuous or discrete. It is represented as s (t). Whenever a signal is represented as a function of frequency, it is called frequency domain representation. It is expressed in terms of efferent frequency components and represented as s (f). Q-4.

What equipments are used to visualize electrical signals in time domain and frequency domain? Mans: Cathode Ray Oscilloscope is used to visualize electrical signals in time domain and Spectrum Analyses used to visualize electrical signals in frequency domain. Q-5. What do you mean by the Bit Interval and Bit rate in a digital signal? Mans: The bit interval is the time required to send one single bit. The bit rate is the number of bit intervals per second. This mean that the bit rate is the number of bits send in one second, usually expressed in bits per second (BSP).