Explain what is dtmf signalling, Computer Engineering

Assignment Help:

Explain what is DTMF signalling.

Dual Tone Multi Frequency (DTMF) was initially introduced in 1963 with 10 buttons into Western Electric 1500 -type telephones. Dual Tone Multi Frequency was originally termed as Touch- Tone. It is a more efficient means than dial pulsing for transferring telephone numbers by a subscriber's location to central office switching the machine. It is an easy two-of-eight encoding scheme, here each digit is represented through the linear addition of two frequencies. This is strictly for signaling among a subscriber's location and message switching center or the nearest telephone office. Dual Tone Multi Frequency is sometimes confused along with other two-tone signaling system termed as multi frequency signaling (Mf) that is a two-of-six code designed to be utilized only to convey information among two electronic switching machines.

Figure demonstrates the four-row-by-four column keypad matrix used along with a DTMF keypad. As in the figure demonstrates, the keypad is comprised of 16 keys and eight frequencies. However, mainly household telephones are not equipped along with the special-purpose keys located into the fourth column (that is the A, B, C and D keys). Hence, most household telephones in fact use two-of-seven tone encoding scheme. The four vertical frequencies which are termed as the low group frequencies are 697 Hz, 852 Hz and 941 Hz and the 4-horizontal frequencies which are termed as the high group frequencies are 1209 Hz, 1336 Hz, 1477 Hz and 1633 Hz. The frequency tolerance of the oscillators is + .5 percent. As demonstrated in figure, the digits 2 by 9 can also be used to show 24 of the 26 letters (as Q and Z are omitted). These letters were originally used to specify one local telephone exchange from other.

255_DTMF Keypad Layout.png

Figure: DTMF Keypad Layout


Related Discussions:- Explain what is dtmf signalling

Explain the client- server interface using procedures, Explain the Client- ...

Explain the Client- Server Interface Using Procedures Developers must realize that client-server impose a division of labor in application programs. Programs must be broken up

What are assets in adobe premiere pro, Question: a) What is the meanin...

Question: a) What is the meaning of the term CTI in Adobe Premiere Pro? b) What are assets in Adobe Premiere Pro? c) In Adobe Premiere Pro, what is the principal diffe

Appropriate problems for ann learning, Appropriate Problems for ANN learnin...

Appropriate Problems for ANN learning: Conversely as we did for decision trees there it's important to know where ANNs are the right representation scheme for such job. Howeve

What are the minimal cost and minimal risksolution, In binary representatio...

In binary representation there are some states that are believed to be never occurred because of some particular functionality of a given circuit. If zero output is assigned to suc

Explain latex in matlab, Matlab already handles naturally easy LaTeX encodi...

Matlab already handles naturally easy LaTeX encodings that permit introducing Greek lettters or modifying the font size and appearance in plots.

Describe the external users of system, Q. Describe the External Users of sy...

Q. Describe the External Users of system? External Users: Modern information systems are now reaching beyond the boundaries of traditional business to involve customers and o

Shared-memory programming model, Q. Shared-memory programming model? In...

Q. Shared-memory programming model? In shared-memory programming model tasks share a common address space that they read and write asynchronously. Several mechanisms like semap

State about the machine language programs, State about the machine language...

State about the machine language programs The computer can run only machine language programs, one needs to translate above programs to machine language programs. To translate

Identify the number of control lines for 16 to 1 multiplexer, The number of...

The number of control lines for 16 to 1 multiplexer is ? Ans. We have 16 = 2 4 , 4 Select lines are needed.

What is minimum spanning tree, Minimum Spanning Tree: Given a weighted gra...

Minimum Spanning Tree: Given a weighted graph G, it is often desired to make a spanning tree T for G, like the sum of weights of the edges in T is the least. Like tree is known as

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