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 the dynamic timing, Explain in detail about the Dyn...

Explain in detail about the Dynamic timing a. Design is simulated in full timing mode. b. Not all possibilities tested, as it is dependent on input test vectors. c. Simul

Time slice, The Linux Process Scheduler uses time slice to prevent a single...

The Linux Process Scheduler uses time slice to prevent a single process from using the CPU for too long. A time slice specifies how long the process can use the CPU. In our simulat

What are escape sequences characters, What are escape sequences characters?...

What are escape sequences characters? List any six of them.  The characters which when used with output functions like printf( ),putc(),put() etc. helps in formatting the outpu

List the properties which a hashing function should possess, List the prope...

List the properties which a hashing function should possess to ensure a good search performance. What approaches are adopted to handle collision? A hashing function h must poss

How do you populate data into a multiple line field, How do you populate da...

How do you populate data into a multiple line field? To populate data into a multiple line field, an index is added to the field name to show which line is to be populated by t

Explain the term overlays, Explain the term Overlays. An overlay is an ...

Explain the term Overlays. An overlay is an element of program that has the same load origin as several other part of the program. These are used for reduce the main memory req

What is polling, What is polling? Polling is a scheme or an algorithm t...

What is polling? Polling is a scheme or an algorithm to recognize the devices interrupting the processor. Polling is employed when multiple devices interrupt the processor by o

Message passing programme development environment, In a multicomputer syste...

In a multicomputer system the computational load amid different processors should be balanced.  To pass information between different nodes message passing technique is used. The p

Determine the output of an even parity generator, When the set of input dat...

When the set of input data to an even parity generator is 0111, the output will be ? Ans. Into even parity generator if number of one is odd then output will be 0.

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