The basic application block diagram of the voice separator is the voice splitter, referred to as the splitter (Splitter), which is applied to xDSL (xDSL is the collective name of various DSLs, that is, the digital subscriber line, which is the transmission technology of the traditional telephone copper wire as the transmission medium, where x Represents different types of DSL technologies, including ADSL++, HDSL, VDSL, etc. in broadband communications. We often say that the splitter only refers to the ADSL (Asymmetrical Digital Subscriber Line) splitter, which is a voice splitter (ADSL over POTS Splitter) that transmits broadband digital signals on a traditional voice telephone line. Now ADSL has Upgrade to the new version of higher speed ADSL++ and VDSL (Very High Speed ​​Digital Subscriber Line).
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The voice separator effectively separates the low frequency audio signal (300~3400Hz) on the line and the high frequency digital modulation signal (20KHz~4.4MHz/12MHz) of the transmitted data, and then sends the audio signal to the PSTN (Public Switched Telephone Network) switch or A POTS (Plain Old Telephone Service) telephone fax machine or the like sends a high frequency digital modulated signal to a DSLAM (DSL Access Multiplexer) / DSL MODEM modem. DSL technology realizes that the user's multiple telephone extensions, fax machines and ADSL modems do not affect each other, that is, isolates the current noise generated by the broadband Internet access in the POTS telephone, ensures high-quality call effects, and avoids broadband caused by telephone ringing. The Internet is dropped, ensuring the download rate of broadband Internet at a certain transmission distance, and so on. Figure 1 is a block diagram of the application of the DSL splitter.
Figure 1 DSL voice separator application block diagram
It can be seen that a voice separator is required in both CO (Central Office or LE, Local Exchange) and CPE (Customer Premise). The user-side separator is generally a box separator and is externally connected to the separator unit according to actual needs. Most of the central splitter 32/48/64 channels are collected on one splitter board, and multiple splitter boards are installed on the central office cabinet, and the control switch board, back board, line interface board and uplink board are realized together. Separation and transmission of voice and digital signals, exchange and management of voice, and convergence of broadband. In addition, there is an overcurrent and overvoltage protection circuit on the separator board to achieve protection functions such as lightning strike, power line contact and induction.
Main indicators of the voice separator
With the popularity and promotion of DSL technology around the world, voice separators have also been widely used. According to the global separator standards, there are ETSI (European Telecommunications Standards Institute), ANSI (American National Standards Institute), BT (British Telecom), ITU-T G.992 (International Union G.992 series) and China MII (Ministry of Industry and Information Technology of the People's Republic of China Ministry of Industry and Information Technology). According to the splitter application, there are mainly ADSL over POTS, ADSL over ISDN, VDSL over POTS, VDSL over ISDN, and the like.
The existing speech separators are multi-stage filter circuits composed of inductors, capacitors and resistive passive devices. The main indicators are POTS insertion loss, POTS reflection loss, group delay, longitudinal balance, band isolation, DSL band insertion loss, etc. .
The insertion loss reflects the degree of signal attenuation of the low-pass filtering and high-pass filtering of the speech separator in their respective passbands, which determines the degree of influence of the splitter on the passing signal. The smaller the loss, the smaller the attenuation through the signal.
The reflection loss reflects the matching degree of the interface impedance of each port of the splitter. The better the matching degree, the smaller the reflection loss, and most of the source signal is transmitted to the load.
The group delay refers to the delay of the transmitted speech signal due to the LC filter circuit of the splitter. The smaller the delay, the better.
Longitudinal balance means that the splitter will have a certain influence on the differential signal due to the asymmetry on the Tip and Ring lines, affecting the integrity of the signal transmission. The greater the vertical balance, the better.
The band isolation reflects the degree of isolation of the two signals when the splitter separates the low frequency speech signal from the high frequency digital signal. The larger the band isolation, the better.
Since the splitter separates low frequency voice signals from the telephone or fax machine, these devices are remotely powered, so the splitter must not drop in product characteristics at the specified feed current. The upper limit of the feed current capability of the national standard ADSL splitter is 100mA, and the European standard splitter is the feed current of the upper limit of 80mA.
Evolution and development of voice separators
From the traditional voice program-controlled switches from the beginning to the modem dial-up Internet, the DSL technology that uses the copper cable to transmit voice signals and high-frequency digital signals is developed. Engineers and technicians around the world have realized the utilization and reuse of the existing copper twisted pair, and the access has shown unprecedented vitality on the existing copper wire. With the application of ADSL technology, ADSL voice splitter is accompanied, and the splitter is accompanied by DSL access technology to experience the evolution and development of low speed to high speed.
Access technologies are mainly divided into wired access and wireless access. Although new access technologies such as FTTx and WiMAX are developing rapidly, DSL access in wired access, along with ADSL to ADSL++ and VDSL/VDSL2 Development, DSL access, in terms of stability, interoperability, transmission speed, transmission distance and saving operator investment (input-output ratio), etc., all reflect the competitiveness that other access technologies cannot match, DSL Still an important force in access technology. Especially in the process of light entering the copper retreat, the main way of transmission of copper wire in the last few hundred meters distance.
In recent years, the global cable access network technology has developed rapidly, and has shown a trend of broadband, IP and service integration. DSL access has also gradually developed into an access platform for streaming media such as IPTV and Triple-Play. The DSL access is closely integrated with the development of home network technology, and the remote management of DSL terminals is gradually realized, and the maintenance cost continues to decrease.
Since the DSL access network needs to effectively separate the traditional low frequency speech signal and the high frequency DSL data signal, a splitter must be used. The DSL splitter application block diagram is shown in Figure 2 below. Usually, the DSL splitter central office equipment supplies power to the user terminal through the telephone line, and the feed voltage is 48V; the feed current flows through the central office and the user terminal splitter, and the feed current is not less than 100 mA according to the national standard YD/T-1187.
From ADSL to ADSL++, and then to VDSL/VDSL2, the band distribution and band expansion of the DSL access technology are shown in Figure 2. According to China's national standards, the ADSL to ADSL++ band extends 30K-4.4MHz from 30K-1104KHz; the VDSL/VDSL2 is extended to 20K-12MHz and 20K-30MHz. According to the European ETSI series of standards, the ADSL to ADSL++ band extends 32K-4.4MHz from 32K-1104KHz; to VDSL/VDSL2, the frequency band is extended to 25K-12MHz to expand 25K-30MHz. The Chinese MII standard is YD/T-1187-2006, and the European standard is ETSI TS 101 952-1(2)-1/2/3/4 and so on.
Figure 2 DSL band distribution and development
In applications to VDSL/VDSL2, the frequency band distribution for splitter applications has been as high as 12MHz/30MHz. The requirements for the separator are higher. Due to the increasing integration density of modern separator plates, the size of the separators is getting smaller and smaller.
Special requirements for new applications and new applications of voice separators
Several typical new applications of DSL technology include IPTV (Internet Protocol Television Internet Protocol) and FTTx (Fiber to the Cabinet or Building or Home).
IPTV is a service that provides an interactive multimedia service for users by using an IP broadband network as a transmission channel and a TV as a terminal. Mainly through a wide-ranging set-top box, connected to the broadband network, watching more rich program channels on the TV, you can order movies, TV dramas, interactive TV, and provide information services, video calls, distance education and other services.
The IPTV service is characterized by interaction, integration, personalization, humanization and enrichment. Referring to Figure 3 below, the relationship between DSL technology and IPTV can be seen.
The new requirement of IPTV for voice splitter is that when the phone rings and voice communication, it will not affect the digital network TV signal, such as frame loss to generate mosaic or display pause. The requirement for the separator is that the separator has a higher feed-through current capability, requires more than 100 mA of feed current capability, and the longitudinal balance of the voice separator is also higher.
The FTTx+DSL application is based on the FTTX technology of the EPON (Ethernet Passive Optical Network) and extends the optical fiber to the ONU (Optical Network Unit) or MDU (Multi-Dwelling Unit) in the cell, building, and corridor. Multi-user Ethernet ONU or multi-user DSL ONU, with DSLAM board or integrated DSLAM to ONU or MDU equipment, provides users with Ethernet interface, DSL subscriber line and Cable line, on the one hand, it can meet various services. On the other hand, because multiple users share the cost of a single terminal, the construction cost is greatly reduced on the basis of the guaranteed bandwidth, and the last one mile of network access is realized.
The network structure diagram of DSL in FTTx (EPON & GPON) is as follows:
The PON+DSL2plus/VDSL/VDSL2 application also puts new requirements on the voice splitter. First, the working bandwidth of the splitter should be extended to 12M/30M, and the working bandwidth of the splitter is higher. Secondly, because VDSL2 expands 30M, it is also subject to external interference, which requires less crosstalk between adjacent channels. In addition, this technology also includes IPTV. Application, the same requires that when the phone rings and voice communication, it will not affect the digital network TV signal, such as frame loss to generate mosaic or display pause, etc., which is the same as DSL application in IPTV.
summary
Tiantong Zhejiang Jingdian Technology Co., Ltd. relies on the advantages of the parent company Tiantong (TDG brand) in the production and development of ferrite core materials, combined with the company's powerful full-process EMS electronic manufacturing service capabilities, to develop a series of high-quality, A miniaturized full range of voice splitter modules and a variety of 32/48/64 voice splitter boards for communications equipment manufacturing customers. The voice splitter and voice splitter board fully meet the market demand and meet the needs of next-generation VDSL technology. It has been applied in batch applications in IPTV and EPON+VDSL applications, and is committed to providing customers with professional technical support to create value for customers.
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