<< Chapter < Page Chapter >> Page >

Block Diagram of Touch-Tone Telephone System

[link] shows the front panel of the touch-tone telephone system. When the program is run, one can hear the dial tone and see the signal displayed in the upper waveform graph. As soon as any number key is pressed, the dial tone is stopped and the corresponding key pad tone is heard and displayed. When keys are pressed 10 times (a valid phone number), the system plays the ringing tone or busy tone depending on the setting and displays the tone in the lower waveform graph.

Front Panel of a Touch-Tone Telephone System

Lab exercises

Dithering

Dithering is a method of decreasing the distortion of a low-frequency signal due to signal digitization [link] . Dithering works best when the sample rate is high in comparison with the rate at which the signal changes.

To see how this works, consider a slowly varying signal and its digitization, shown in [link] (a). If noise is added to the original signal amplitude roughly at one half the step size, the signal will look like [link] (b). If the digitized signal is passed through a resistor-capacitor circuit to smooth it out, an approximation to the original signal can be recovered. There is no theoretical limit to the accuracy possible with this method as long as the sampling rate is high enough.

Design a system to analyze the dithering technique. First, show the digitized and smoothed signal without dithering. Then, add random noise to the input signal (noise level should not exceed 50 percent of the step size of the digitized signal) and show the digitized and smoothed version. Measure the maximum and average error between the original signal and recovered signal.

Processing at One Half-Step Size: (a) From Top, the Original, Digitized and Smoothed Signal without Dithering, (b) From Top, the Noise Added, Digitized and Smoothed Signal with Dithering

Insert Solution Text Here

Image Processing

DFT is widely used in image processing for edge detection. A digital image is a two-dimensional signal that can get stored and processed as a two-dimensional (2D) array. In the frequency domain, with the center denoting (0,0) frequency, the center portion of this 2D array contains the low-frequency components of the 2D signal or image. The edges in the image can be extracted by removing the low-frequency components.

Read and display the image file image1.jpg provided on the book website. Then, complete the following steps:

  1. Compute and display the 2D DFT of the image using the LabVIEW MathScript functions fft2 and fftshift .
  2. Remove the low-frequency components of the image. A user-controlled threshold can be specified to remove a varying amount of the low-frequency components.
  3. Compute and display the inverse 2D DFT of the image using the LabVIEW MathScript functions ifft2 and fftshift . The processed image should reflect the edges in the original image.

Insert Solution Text Here

DTMF Decoder

Design a decoder VI for the DTMF system described in Telephone Signal section. The VI should be capable of reading the touchtone signal as its input and display the corresponding decoded key number as its output.

Insert Solution Text Here

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, An interactive approach to signals and systems laboratory. OpenStax CNX. Sep 06, 2012 Download for free at http://cnx.org/content/col10667/1.14
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'An interactive approach to signals and systems laboratory' conversation and receive update notifications?

Ask