Sistem TeleponPertemuan 11

Matakuliah : H0122 / Dasar TelekomunikasiTahun : 2008

2Bina Nusantara

Mahasiswa dapat menunjukkan konsep telepon, bagaimana koneksinya serta

masalah yang ada pada sistem telepon.

Learning Outcomes

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• Terminology• Central Office• Switching

Outline Materi

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•Terminology– Local loop– Central office– Exchange– Trunk– Nodes– Super trunks– Tandem

switch– Hierarchy

Telephone System

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• Three major components:– Local loops: twisted pair, analog signaling– Trunks: fiber optics or microwave, mostly

digital– Switching offices

Local Loop

End Office

Trunk

Toll Office Switching Office

IntertollTrunk

Components

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Hierarchy

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•Telephone Terminal– Local loop and Basic Phone – Calling sequence in phone

•Talking signals– Analog voltage

•Outgoing : 1 – 2 V at approx. 3 mA• Incoming : half of outgoing

signals•Local loop characteristics

– Envelope delay– Voice grade:

•Dial-up or switched line•Dedicated, conditioned or leased

line

Terminal/Local Loop

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•Loop signal level– Outgoing : - 10 and 0 dBm (600 )– Incoming : - 42 to – 4 dBm– Termination on the Central office : 600

(or 900)•Dialing

– Pulse– Tone

•Dual-tone multi-frequency (DTMF)

Terminal/Local Loop

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DTMF tones for each number

Terminal/Local Loop

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•BORSHT is the function of Subscriber loop interface circuit (SLIC) or line card in interfacing to a local loop– Battery : - 48 V dc– Over voltage : protection from excessive

voltage– Ring trip : send 90 V 20 Hz ac signal with on

hook : 2 s ; off hook : 4 s– Supervision : monitor the phone loop– Hybrid:

•Two-wire to four-wire converter or four wire terminating set: plit the local loop into 2 wire pairs.

•Trans-hybrid loss: – 30 to 50 dB of rejection– Test

•To test signals on the line and to check quality of loop and phone performance

Loop Supervision

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• Process calling :– Recognize the dialed digits– Make physical connection

• Connection :– Allow an analog signal voltage – Switching systems in matrix (crossbar or

cross point switch)– For greater reliability used reed relay

Central Office

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Common Channel Signaling

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•Echo parameters:–Signal travel time and travel distance–Echo time = (distance/prop.velocity) x 2

•To Cancel –Insert the reverse path loss

•Echo suppression by insertion of reverse path loss

–Signal subtractions•Echo suppression using the signal subtraction method

–Digital signal processing•New version of subtraction method, need arithmetic calculation (algorithm)

–Four-wire method

Echo Cancellation

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Echo Cancellation

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Four Wire

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• Telah dipelajari gambaran umum sistem telepon.

• Telah dipelajari komponen telepon.

Summary