TelephonyNguyn Duy Nht Vin

Chapter 2Subscriber Line and Digital Trunk in the Telephone Network

ng dy thu bao

Page *S khi chc nng ca in thoi tng tMch thoiMch quay s

SwitchhookMch bo vMch chungGi TTipRingRLocal Exchange

Page *Trng thi nhc / t t hp:Thu bao nhc / t t hp mch vng thu bao ni vi mch thoi v quay s hoc mch chung.Tr khng nhc my danh nh: 400Tr khng t my danh nh: 1600.

text

DC

RCL

RT

SLIC

RL

ng dy in thoi

T hp in thoi

Tng i

RT: Telephone RessitorRL: Line ResistorRCL: Current Limiting Resistor

-48VDC

Page *Quay s bng xung thp phn

Page *Quay s bng xung thp phnS quay tng ng vi s xung gi i.(s 1 1 xung, s 9 9 xung, s 0 10 xung)Chu k mi xung l 100ms.Thi gian quay s lu, ph thuc vo ch s quay.Khng quay s c trong khi m thoi.

100msHRLR

IL

1

2

3

Page *Quay s bng DTMFDTMF (Dual Tone Multi-Frequency)Mt s tng ng vi hai tn s, cc tn s ny t tn ti trong m thanh t nhinThi gian quay s nhanhC th quay s khi m thoi

1

2

3

4

5

6

7

8

9

*

0

#

A

B

C

D

697Hz

770Hz

852Hz

941Hz

1029Hz

1336Hz

1477Hz

1633Hz

Page *Tn hiu chungTn hiu xoay chiu, in p 40 130V, tn s 16 60Hz.Ngt qung 2s:4s hoc 0.4s:0.2s:0.4s:2s.

Bin

Bin

t

t

2s ON

2s ON

4s OFF

2s OFF

0.4s ON

0.4s ON

1s

0.2s OFF

2s OFF

Bc M v nhiu nc khc

M

Page *Mch chung

Chnh lu ton sng(Full-wave Rectifier)

n p

Suy gim

Lc thng thp

in p chun

-

+

To a m

TIP (T)

RING (R)

So p

Cung cp p cho mch chung

Page *Giao tip thu bao trong tng iRing RelayOvervoltageProtectionCircuitSLIC(SubscriberLoopInterfaceCircuit)CODEC(Encoder/Decoder)TSAC(Time SlotAsignmentCircuit)TxRxTc bitTn s ly muRxETxEHSO(Hook Status Output)RE(Ring Enable)in p vo75VAC, 25Hzin p voDC, cp ngunAnalog DigitalGiao tip thu baoPDPower DownTx: TransitRx: ReceiveTxE: Tx EnableRxE: Rx EnableCPU

Page *Giao tip thu bao trong tng iCc chc nng : BOSRCHTChc nng cp ngun B (Battery)My in thoi thu bao yu cu cp ngunThc hin bi SLIC t in p (48V) ca ngun 1 chiu.Ngun cp dng ngun dng, dng in khong 20-100mAYu cu hn ch tp m v nh hng thoi n cht lng ngun 1 chiu

Page *SLICGiao tip thu bao trong tng iChc nng cp ngun B (Battery)48VDCTRLine InterfaceDng in mch vng thu bao

Page *Giao tip thu bao trong tng iChc nng bo v qu p O (OverVoltage Protection)Bo v khi c in p cao xut hin trn ng dy nh st, in p cm ng, chp ng dy thoi vi ng dy in p li ...S dng cc bin php: ng phng, ht n ni vi t, gi u dy, diode, bin p cch ly ... Yu cu thi gian phng in nh hn 1 ms.

Page *Giao tip thu bao trong tng iChc nng bo v qu p O (OverVoltage Protection)

Page *Giao tip thu bao trong tng iChc nng rung chung R (Ringing)in p xoay chiu 75VAC, 25Hz.Thng s dng rle cp chungYu cu pht hin thu bao nhc my khi chung.Tn hiu chung c iu khin bi TSAC

Page *Giao tip thu bao trong tng iChc nng rung chung R (Ringing)

Pht hin nhc my

Page *Giao tip thu bao trong tng iChc nng gim st S (Supervision):c thc hin bi SLICDa vo in tr mch vng nhn bit cc trng thi nh quay s, nhc, t my... S dng cc photo-diode cch ly masse tng t v s Yu cu chnh xc, chu k qut nh hn s bin ng ca xung quay sHSO ch th trng thi nhc t my ca thu bao

Page *Giao tip thu bao trong tng iChc nng gim st S (Supervision):IL

Page *Giao tip thu bao trong tng iChc nng m ha C (Coding)c thc hin bi mch CODEC.Chuyn i tn hiu thoi sang PCM v ngc li.Cn c cc tn hiu syn, clock vo v ra

PD

Page *Giao tip thu bao trong tng iChc nng sai ng H (Hybrid) c thc hin bi SLIC chuyn i hai dy sang 4 dy.Hn ch ting vng bng mch cuS dng bin th cch ly kt hp vi in tr cn bng hoc IC.

Pht

Thu

Mch cn bng

Hai dy thoi tng t

Hai dy Codec

Hai dy Decodec

Page *Giao tip thu bao trong tng iChc nng sai ng H (Hybrid)

Thu

Pht

Thoi tng t

CODEC

-

-

+

+

Page *Giao tip thu bao trong tng iChc nng kim tra T (Test):Tng an ton v tin cy ca tng i Mi dy thu bao phi c kh nng kim tra.Kim tra c th thit lp/ gii to theo yu cuTruy cp gia giao tip thu bao v thit b kim tra c th qua bus hay qua khi chuyn mch.Test in: Bin dng tn s, tiu hao i v, dng in mch vng, o nh cc, pht hin m mi quay s, ct dng chung...Test out: o th in p xoay chiu, in p 1 chiu, cch in, in dung gia trip - ring trip, ring - t v cc m thanh pht ti thu bao ang t t hp...

Page *Bo hiu mch vng thu baoKhi nim:Thit lp ni kt gia hai thu bao thuc tng iBo hiu c chuyn i qua li gia thu bao tng i thu bao trn chnh i dy mang tn hiu thoi gm:Tn hiu gim st (trng thi): Gim st trng thi ng dy thu bao t khi thit lp n lc gii ta.Tn hiu a ch (quay s): S in thoi ca thu bao b gi.

Page *Bo hiu mch vng thu baoTin trnh gi tiu biu:

Giao tip trung k

Page *Khi nimTrung k l cc tuyn truyn dn gia cc tng i PSTN.T nm 1960, cc trung k tng t c s dng ni gia cc tng i. Cc trung k ny da trn c s mch vng thu bao.Trung k tng t bao gm hai dy tip (T) v ring (R) mang tn hiu thoi cn bng hai hng.Nhu cu gi tng, yu cu tng cc tuyn v khong cch cc trung k.Gii php: Ghp knh.

Page *Giao tip trung k s

Giao tip trung k s

Thoi s ha

n tng i khc

T tng i khc

Trung k s (4dy)

Hai dy

Chuyn mch s

Bo hiu

Thoi s ha

Bo hiu

X l cuc gi

Page *S khi chc nng

Kt cui thu

Gii m ng dy

m ng b khung

Tch bo hiu (CAS, hoc CCS)

Chuyn i ni tip/song song

Chuyn mch bo vTX

Tch nh thi

Tch ng b khung

8

8

8

...

n Chuyn mch s

DDF

Kt cui pht

M ha ng dy

Chn bo hiu (CAS, hoc CCS)

Chuyn i song song/ni tip

Chuyn mch bo vRX

8

8

8

...

T Chuyn mch s

ng h Tng i

Thu/pht bo hiu (CAS hoc CCS)

DLTU

T Tng i khc

n Tng i khc

nh thi ghi

nh thi c

Page *S khi chc nngM ha/Gii m ng dyChuyn i tn hiu t nh phn sang ng dy v ngc li.H thng cp ng thng dng cc m ng dy nh HDB3, 4B3T, B8ZS hoc AMIH thng si quang thng dng m 4B5B.H thng chuyn mch s dng tn hiu PCM Chuyn i qua li.Thc hin gii m ng dy yu cu ng h bit t mch Tch nh thi.

Page *S khi chc nngAMI: Cc bit 0: khng truyn tn hiu.Cc bit 1: truyn xung vi cc tnh thay iB8ZS: tn hiu s l tn hiu AMI nhng c 8 bits 0 lin tc c thay bng chui xung cha 2 bit phm lut .HDB3: tn hiu s l tn hiu AMI nhng c 4 bits 0 lin tc c thay bng chui xung cha 1 bit phm lut.Trong : B l bit 1.

1

1

Binary

AMI

B8ZS

HDB3

1

0

0

0

0

0

0

0

0

Page *V dSn ln ca ng h bit c khi phc c xp gia xung ca tn hiu s nhiu nhn c.Ch : Mch khi phc d liu/ng h pht hin c tn hiu nhn c t trung k hay khng.

Page *S khi chc nngng b khungPht hin khung qua phn tch tn hiu t gii m ng dy tm im bt u khung: TS0.Cn thit khi phc chnh xc d liu thoi v d liu s trong cc khe thi gian mi khung.B m c s dng ng b cho cc ng dy khc nhau.Lung PCM c ghi vo b m vi tc xc nh t b tch nh thi v ng b khung.Ni dung trong b m c c ra ng b bi ng h tng i a n Chuyn mch c ng b gia cc ng.Khng cn thit theo hng pht v vic nh thi v ng b cho tt c hng ny c thc hin trc tip bi chnh tng i.

Page *S khi chc nng

Khung

Khung

Khung

Khung

m ng b khung

m ng b khung

m ng b khung

m ng b khung

nh thi ghi

nh thi ghi

nh thi ghi

nh thi ghi

nh thi Tng i

Khung

Khung

Khung

Khung

nh thi c

nh thi Tng i

Page *S khi chc nngChuyn i ni tip/song songYu cu v Chuyn mch s hot ng vi 8 bits song song.Chuyn mch bo vTy thuc theo h thng c yu cu hay khng m phng v trn hai mt phng song song ca Chuyn mch s (d phng).Chuyn mch bo v cho hng thuGim st m kim tra trn cc ng dn (v d to m CRC)Xc nh v chuyn mch gia cc ng dn Chuyn i Cnh bo trn hai mt phng chuyn mchChuyn mch bo v cho hng phtTo m kim traChia tn hiu pht thnh hai dng bit c lp.

Page *S khi chc nngTch/ghp bo hiuTy thuc h thng PCM (32, 24).Ty thuc h thng bo hiu (CAS, CCS).Tch/ghp thng tin bo hiu trong khe thi gian thch hp (TS16) a n b thu pht bo hiu (CAS, CCS) c nh tuyn qua Chuyn mch s.Kt cui thu/phtChuyn i tn hiu ph hp vi u cui a dng ca trung k.Chun thng dng: G703.

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