Carry business and user terminal business

Definition: Bearer service
User Terminal Service teleservice is also called "complete telecommunication service ".It refers to the term indicating the basic communication nature. It means that the communication content is not understood during communication, but data is transmitted as a bit stream. In contrast, in services such as fax and email, the network side needs to read the control information in the data to control it. This kind of service, called teleservice, is developed from telephone. Description: There are two types of telecommunication services: basic services and supplementary services ). Basic services can be divided into bearer services that provide basic transmission functions and teleservices that include terminal functions ). The bearer service provides a means to transmit information between users in real time without changing the content contained in the information. Such services correspond to the low-layer functions of the Open Systems Interconnection (OSI) Reference Model. The user terminal service combines the transmission and information processing functions to not only provide OSI's low-level features, but also provide high-level functions (hLF ). If the bearer service defines requirements for network functions and network functions provide such services, user terminal services include both terminal capabilities and network capabilities. Both the bearer service and the user terminal service can work with the supplementary service to provide services for users. However, the supplementary service can work with one or more bearer services or user terminal services and cannot be used independently. The bearer service only describes the communication capability of the communication network, but is irrelevant to the type of the terminal. Therefore, different types of terminals can use the same bearer service. User Terminal Services include the communication capability provided by the network and the communication capability of the terminal itself. The user terminal business can be understood as the business obtained by the user through the communication of the terminal. When using the basic services that carry the business and the user terminal business, you can also require ISDN to provide additional functions. This additional functionality provided by the network is called complementary services. Supplementary services cannot be provided to users independently. They must be provided along with basic communication services. Next we will give a more detailed introduction to these three types of services: 1. Carry the services

The bearer service is provided at the ISDN User/network interface and is unrelated to the user terminal type. This service is divided into three types: the bearer service of circuit switch, the bearer service of group switch, and the bearer service of frame mode.
The bearer services of circuit switching are 3. lkhz audio, 64 kbit/s unrestricted digital information, voice, 2 × 64kbit/s unrestricted digital information, 7 Khz audio, 384 kbit/s unrestricted digital information, 1920 kbit/s unlimited digital information and video.
The packet exchange bearer services include grouped data services that are connected through B-Channel Exchange, data services that use B-Channel group exchange and data services that use d-Channel group exchange, virtual calls and permanent virtual circuits can be provided, and users can communicate through ISDN in a point-to-point manner according to the x25 protocol.
Frame-based bearer services are dividedFrame RelayAnd frame switching. Anti-frame service is mainly used inData CommunicationIs a new type of ISDN bearer service that has developed rapidly recently.

2. User Terminal Services

User Terminal business refers to all user-oriented application businesses. There are many types of user terminal services, mainly including: (1) digital phones. Compared with analog phones, digital phones have advantages such as good quality, high definition, high signal-to-noise ratio, and unlimited transmission distance. (2) videophone. It is a communication service that integrates computer, telephone, and television technologies, so that people in two places can communicate face to face without leaving the house. (3) four types of faxes. The G4 fax machine is a high-speed fax machine, which greatly improves the transmission rate and quality compared with the G3 of the three types of fax machines. It can transmit an A4 file in 3 seconds. (4) data communication. The 64 kbit/s or 128 kbit/s data communication provided by ISDN is more reliable than the current DDN data communication, and supports simultaneous data transmission and telephone communication. (6) Conference and television. Generally, the conferencing and television business is to connect three 2B + D devices to conferencing and television devices through MCU re-connection, so as to achieve remote third-party teleconference through dialing.

3. Supplementary Services

This service can be divided into direct dial-in, multi-user number, and caller line identification, main Call Line Identification restrictions, provided by wiring identification, restricted by wiring identification, malicious call identification, sub-address, pre-transfer in case of busy call, meta-response call forwarding, unconditional call forwarding, Terminal mobility, call waiting, call persistence, third-party services, conference calls, and user-user signaling. The specific services are as follows: (1) multi-user numbers. For non-ISDN users, a single user line can have only one phone number. ISDN users can use a pair of common telephone lines to allocate multiple user numbers, which are assigned to different terminal devices. In this way, the user can make multiple terminals connected to the same telephone line have different phone numbers without paying extra line numbers. (2) subaddress. It is a performance that is applied to the call end. Although ISDN can be automatically selected based on the terminal type during communication, if multiple terminals of the same type are connected to the called end, several digital phones will ring at the same time. With this performance, you can set sub-addresses on different terminal devices and use sub-addresses to differentiate different terminals. When the caller has a sub-address number, only the user with the same sub-address can ring the bell. (3) Forward call. When a call is made to a called USER, if no response is received within the specified period of time, the call is sent to another predefined number. When a user initiates an unconditional call, all calls to the user are forwarded to another pre-set phone number unconditionally. The call performance of this user remains unchanged. (4) call transfer. Transfers a called call to another user. (5) billing notification. This service provides users with billing information. It has three methods: notification rate at the start of a call; notification of the fees incurred when a call is made; total fee of notifying the call when the call ends. (6) User-user signaling. The user sets and stores some information on the phone, sends the information to the other party in the form of data, sends the information to the other party on the digital phone display of the other party. This service is mainly used to send and receive information through D. When two B channels are occupied at the same time, this service can still take effect.