Explain simple telephone communication system, Computer Engineering

Assignment Help:

Explain simple telephone communication system with circuit and equation of current flow in microphone?

Simple Telephone Communication: In the simplest type of a telephone circuit, there is one method communication including two entities, one receiving (listening) and another transmitting that is talking.

2055_A Simplex Telephone Circuit.png

FIG - A Simplex Telephone Circuit

Simplex communication: The earphone and microphone are the transducer components of the telephone communication system. The earphone converts the electrical signals in audio signals and Microphone converts speech signal to electrical signals. Most usually used microphone is carbon microphone. Carbon microphones do not generate high fidelity signals, but provide out strong electrical signals at acceptable quality levels for telephone conversation. A certain quantity of small carbon granules is placed in a box, in carbon microphones. Carbon granules conduct electrically and the resistance offered through them is dependent on the density with that they are packed. One side the box is covered is flexible and is mechanically attached to a diaphragm. While sound waves impinge upon the diaphragm, this vibrates, causing the carbon granules to compress or expand, therefore changing the resistivity offered through the granules. If a voltage is applied to the microphone, the current in the circuit varies as per to the vibration of the diaphragm.

While the sound waves impinge on the diaphragm, the instantaneous resistance of the microphone is specified by

ri = r0 - r sinωt

Where

r0 = Quiescent resistance of the microphone while there is no speech signal.

r = Maximum variation in resistance offered through the carbon granules, r < r0.

The negative sign shows that when the carbon granules are compressed the resistance reduces and vice versa. Avoiding impedances external to the microphone in the circuit specified in figure without loss of generality, the instantaneous current in the microphone is specified by

i = V/(r0 - r sin ωt) = I0(1 - m sin ωt)-1

 Here I0 = V/r0 = Quiescent current in the microphone. m = r/r0 , m < 1

 Through binomial theorem, the equation may be expanded as i = I0 (1+ m sin ωt + m2 sin2 ωt + ....)

When the value of m is adequate small that is usually the case in practice, higher- order terms can be avoided in the above equation giving as:

i = I0 (1+ m sin ωt)

Therefore, the carbon granule microphone functions as a modulator of the direct current I that is analogous to the carrier wave in AM system. The quantity m is equal to the modulation index in AM.


Related Discussions:- Explain simple telephone communication system

Explain in detail about register transfer language, We have multiple instan...

We have multiple instances in RTL (Register Transfer Language), do you do anything special during synthesis stage? Whereas writing RTL(Register Transfer language),say in Verilo

Define various classes of interrupts, Q. Define Various classes of Interrup...

Q. Define Various classes of Interrupts? Figure below gives list of some common interrupts and events which causes occurrence of those interrupts. Figure: Various clas

Physical characteristics and access mode of disk drive, Q. Physical charact...

Q. Physical characteristics and access mode of disk drive? Access Time: Access time is time needed between requests made for a read or write operation until the time data are

Color scheme in a repeater control, How can you provide an alternating colo...

How can you provide an alternating color scheme in a Repeater control?  AlternatingItemTemplate Like the ItemTemplate element, but rendered for every otherrow (alternating item

Android mobile application, Students are needed to work in group of 3 and m...

Students are needed to work in group of 3 and make an Android mobile application falling under the following categories: Multimedia o    Eg: Camera app, mp3 player, ga

What is virtual memory, What is virtual memory? Virtual memory is a met...

What is virtual memory? Virtual memory is a method used in some large computer systems that allow the user to construct program as by a large memory space were available, equal

Explain the do while loops, Explain The do while loops The do while loo...

Explain The do while loops The do while loops is similar, but the test occurs after the loop body is executed. This ensures that the loop body is run at least once.

What is java applet, A Applet is a java program that runs within a web brow...

A Applet is a java program that runs within a web browser.

Explain XLAT instruction with help of example, Q. Explain XLAT instruction ...

Q. Explain XLAT instruction with help of example? Let's presume a table of hexadecimal characters signifying all 16 hexadecimal digits in table: HEXA      DB      '012345678

Visual perception problems, In AI the process of perception is studied ...

In AI the process of perception is studied as a set operations. A visual scene may be encoded by sensors and represented as matrix of intensity values. These are processed b

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd