sistem telepon pertemuan 11 matakuliah: h0122 / dasar telekomunikasi tahun: 2008
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2Bina Nusantara
Mahasiswa dapat menunjukkan konsep telepon, bagaimana koneksinya serta
masalah yang ada pada sistem telepon.
Learning Outcomes
4Bina Nusantara
•Terminology– Local loop– Central office– Exchange– Trunk– Nodes– Super trunks– Tandem
switch– Hierarchy
Telephone System
5Bina Nusantara
• 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
7Bina Nusantara
•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
8Bina Nusantara
•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
10Bina Nusantara
•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
11Bina Nusantara
• 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
13Bina Nusantara
•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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