Voice service notes

PSTN(Public Switched Telephone Network ): Public switched telephone network （ Voice network ）

IMS(IP Multimedia Subsystem),IP Multimedia system , Now the network used by operators to carry voice .

PBX: The telephone service network used within the company ,PBX Commonly known as SPC exchange , Program control PBX , Telephone switch , Group telephone, etc .PBX It is a kind of telephone communication management means commonly used in modern office , It enables the telephone manager to manage external incoming calls and internal outgoing calls in a group .

DID（Direct-Inward-Dialing）： Direct dial in PBX system services .

function ： A telecommunications company assigns multiple phone numbers to one or more phone lines , This allows the customer to assign a phone number to each employee , But there is no need to lay another telephone line for each employee . In this way , Can easily divert and manage phone traffic . Use DID, Need to buy one ISDN Or digital lines , Then ask the telecom company to assign some telephone numbers , And have DID Functional devices .

1、30B+D（ Self throw 、 There are two ways of investment ）

B passageway ： A channel that carries traffic , such as ： To transmit data 、 Sound and other .

D passageway ： A channel that carries signaling information , such as ： Transmit control and signal information .

30B+D Digital trunk line Refer to , Users occupy a E1（ namely 2Mbit/s） port , Access user switching equipment , Provide users with a fully transparent transmission channel to connect 30B+D, The PBX passes through E1 The line is interconnected with the local terminal , Each root E1 Have 30 User channels and 1 Signaling channels , The protocol is transmitted through signaling , A piece of E1 Can also provide 30 Road voice , Provide N A pilot number ,( It is equivalent to applying for N A direct line telephone ).

E1: Europe's 30 Pulse code modulation PCM abbreviation E1, Our country adopts European E1 standard .E1 A time division multiplexing frame of （ Its length T=125us） It is divided into 32 Equal time slot , The slot number is CH0~CH31. In which time slot CH0 For frame synchronization , Timeslot CH16 Used to transmit signaling , be left over CH1~CH15 and CH17~CH31 common 30 Time slots are used for 30 A way to talk . Transmission per time slot 8bit, So it's shared 256bit. Transfer per second 8000 A frame , therefore PCM A group E1 The data rate is 2.048Mbit/s.

PCM（Pulse Code Modulation, Pulse code modulation ）： Is to put a continuous time , Analog signals with continuous values are transformed into discrete time signals , The value of discrete digital signal is transmitted in the channel . Pulse code modulation is to sample the analog signal first , And then quantize the sample amplitude , The process of coding .

Pulse code modulation can provide users with a variety of services , Both can be provided from 2M To 155M Speed digital data leased line service , Voice can also be provided 、 Image transmission 、 Distance learning and other services .

Trunk line It refers to switches and switches 、 The line connecting line between the switch and the PBX .

characteristic ：

One 30B+D, Realization 30 Simultaneous incoming and outgoing voice calls . Users can use the switchboard + Call by extension ; Distribute 8 Give a real number to the extension , External users can directly 8 Tag number dialing extension , You can also dial the switchboard and then transfer to the extension. The extension can make a direct call , And the real calling number can be displayed , The same number can be displayed , The assigned extension number can also be displayed .

advantage ： Can realize the cornet Mutual dialing , example ：66662000~66664000 The numbers between segments are under the same switch , You only need to dial the last four digits when dialing numbers .

Ratio of subscriber line and trunk line ：8：1.

2、Centrex Business

Centralized PBX , Also called virtual switch , Divide some users into a group on the local user switch .

2.1AG

AG Integrated access gateway .

2.2PON        

No information found

2.3SIP

It is a kind of from the Internet IP Voice session control protocol , Have flexibility 、 Easy to implement 、 Easy to expand .

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