Explain about simplex communication, Electrical Engineering

Assignment Help:

Q. Explain about Simplex communication?

Simplex communication: Microphone and the earphone are transducer elements of the telephone communication system. Microphone converts speech signal to electrical signals and earphone converts the electrical signals into audio signals. Most commonly used microphone is carbon microphone. Carbon microphones don't produce high fidelity signals however give out strong electrical signals at acceptable quality levels for telephone conversation. In carbon microphones, a certain quantity of small carbon granules is placed in a box. Carbon granules conduct electrically and resistance offered by them is dependent upon the density with which they are packed. One side the box is covered is flexible and is mechanically attached to a diaphragm. When sound waves impinge on the diaphragm, it vibrates, causing carbon granules to compress or expand so changing the resistivity offered by the granules. If a voltage is applied to the microphone, current in the circuit varies according to vibration of the diaphragm.

When sound waves impinge on the diaphragm, instantaneous resistance of microphone is given by r,

i= r0- r sin ωt

Where

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

r = Maximum variation in resistance offered by the carbon granules, r 0 .

Negative sign indicates that when carbon granules are compressed the resistance decreases and vice versa. Ignoring impedances external to microphone in the circuit given in figure. without loss of generality, instantaneous current in the microphone is given by

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

Where

 I0= V/r0= Quiescent current in the microphone.

 m = r/r0, m < 1

By binomial theorem, the Eq. may be expanded as

i = I0(1+ msinωt + m2sin2ωt + ....)

If value of m is sufficient small that is typically the case in practice, higher order terms can be ignored in the above Eq. Giving thereby

  i = I0 (1+ m sin ωt)

Therefore  carbon  granule  microphone  acts  as  a  modulator  of  direct  current  I which is analogous to carrier wave in AM system. Quantity m is equivalent to the modulation index in AM.


Related Discussions:- Explain about simplex communication

Digital control system, a digital computer controlled rolling mill regulato...

a digital computer controlled rolling mill regulator system..

Provide definition of signals, Provide Definition of Signals A continuo...

Provide Definition of Signals A continuous-time signal x(t) is a signal that is a function of real number t. For a discrete-time signal x[n], it is a method of discrete time in

Use of a k map simplify the following boolean expressions, Q. With the use ...

Q. With the use of a K map, simplify the following Boolean expressions and draw the logic diagram.

Miller sweep circuit, PlZ Explain broooooo ..? What is Miller circuit and b...

PlZ Explain broooooo ..? What is Miller circuit and bootstrap I have xm tomrow and I am not getting answers soo plz.

Several forms of interference, Q. Several forms of interference? Interf...

Q. Several forms of interference? Interference may take several forms: ac hum, higher frequency pulses and "whistles," or erratic waveforms commonly known as static. Interferin

Digital Signal Processing, Can you do a survey paper on Wavelet and Subband...

Can you do a survey paper on Wavelet and Subband Coding? I need 10 pages and I will provide the references.

Competition, how to be prepare for gate....

how to be prepare for gate....

Steps to develop microprocessor based computer system, Explain in brief ste...

Explain in brief steps to develop a Microprocessor based computer system. The design of a microcomputer system should begin with the CPU module. It modules establishes the fund

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