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

Show the subtraction method, Q. Show the Subtraction Method? For this p...

Q. Show the Subtraction Method? For this procedure (method), start with a weighted position value greater that the number. If the number is greater than the weighted position f

Advantages of software defined radio, Advantages of SDR 1. Easy to upgr...

Advantages of SDR 1. Easy to upgrade 2. Great flexibility. It can be dynamically updated with new software without any changes in hardware 3. Due to reduced number of har

Explain the energy bands in solids, Explain the energy bands in solids. ...

Explain the energy bands in solids. There are as several energy bands in a solid as there are energy levels in the parent atoms. Many electrical properties of significance

Network theorems.., how to calculate voltage when 3 voltage sources are giv...

how to calculate voltage when 3 voltage sources are given?

List the various addressing modes present in 8086, List the various address...

List the various addressing modes present in 8086? There are 12 addressing modes are present in 8086. They are, (a) Register and immediate addressing modes _  Register ad

Sketch the frequency response, Q. For the circuits shown in Figure, sketch ...

Q. For the circuits shown in Figure, sketch the frequency response (magnitude and phase) of ¯V out / ¯V in .

Saturation and cutoff in bipolar junction transistor, Saturation and Cutoff...

Saturation and Cutoff in bipolar junction transistor: Saturation : With both of the junctions forward-biased, a BJT is in saturation mode and makes easy high current condu

EMF, what is induced EMF & what is statically EMF explain in details.

what is induced EMF & what is statically EMF explain in details.

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