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Telecom Switching Systems &Networks

CS/EEE/INSTR C 414

Rahul Singhal

Chamber:

Room No. 2140 (Optical Communication Lab.)

E-mail:

rahulsinghal@bits-pilani.ac.in

Web Page:

http://discovery.bits-pilani.ac.in/discipline/eee/rahul/index.htm

Lectures (PDF) shall be available at:

http://discovery.bits-pilani.ac.in/discipline/eee/rahul/page7_telecom.htm

Notices:

http://discovery.bits-pilani.ac.in/discipline/eee/rahul/page9_notice_telecom.htm

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History

490 BC Heliographs.

2400 BC Postal Systems.

3000 BC Drums and Horns.

16th Century Maritime flags.

1792 Semaphore systems.

1839 first commercial electrical telegraph.

1866 first transatlantic telegraph cable.

1876 telephone (acoustic telegraph).

Antonio Meucci, 1854,constructed telephone-likedevices.

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Meuccis Idea

Charles Bourseul, 1854

Make and break telephone

transmitter and receiver

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Johann Philipp Reis, 1860,constructed prototype'make-and-break' telephones,today called Reis' telephones.

Reis Telephone : Voice and Data Integrated

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Elisha Gray, 1876,designed a telephoneprototype in Highland Park,Illinois.

Alexander Graham Bellwas awarded the U.S.patent for the inventionof the telephone in 1876.

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Alexander Graham Bell with a prototype telephone, 1876.The single-port design required the user to alternately speakinto and then listen through the same equipment or device

Telephone

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Inside the telephone

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Pusks Tivadar (1844 1893) was the first person to suggestthe idea of a telephone exchange

Operation of a ConventionalTelephone

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Subscriber Signaling

Pulse dialing

Usually 10 pulses per second.Interdigit gap at least 200 ms.

Duty cycle: 33%.

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Rotary/Pulse Dialing

Tone Dialing DTMF Pad and Frequencies

1 2 3 A

4 5 6 B

7 8 9 C

* 0 # D

Dual Tone Multi-frequency (DTMF)

1209 1336 1477 1633

697

770

852

941

Timing:Timing:

60 ms Break60 ms Break

40 ms Make40 ms Make

All frequencies in HzAll frequencies in Hz

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DTMF

The pair of frequencies are chosen so that theycan not be mimicked by the human voice easily,which could otherwise interfere with the normalnetwork signaling function.

These tones also can be transmitted through thenetwork and so can be used for various kinds ofremote functions such as remote banking (end-to-end signaling).

History

http://www.cclab.com/billhist.htm

http://en.wikipedia.org/wiki/History_of_telecommunication

http://en.wikipedia.org/wiki/History_of_telephone

http://en.wikipedia.org/wiki/Timeline_of_the_telephone

http://www.tematelecom.net/upload_images/Indian_Telec

om_History.pdf

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1876 Edison tests his first carbon microphone.