What Are Exchange Controls?

Switching control modes refer to the manner in which the switching logic of a switch is controlled by signaling and control logic.

Switching control modes refer to the manner in which the switching logic of a switch is controlled by signaling and control logic.

Chinese name

Exchange control method

Foreign name

switchingcontrol modes

Applied discipline

Communication

Classification of exchange control methods

The function for performing the switching operation is directly connected to the decentralized communication channel, and its action law and mutual connection can be summarized as the switching logic. The functional parts used to analyze the signaling to control the switching function are generally set up centrally and used for public use, and their action laws and interconnections can be summarized as control logic. Control logic is closely related to telecommunication services, also called business logic. According to the control method, the control logic is divided into two types: direct decentralized control and indirect centralized control.

1.1 Direct decentralized control

Also called direct step-by-step control. There is no special control function, and a certain digit of user signaling directly controls the connection component. The circuit extends to the next level or next switch, and the digits are repeated until the last two digits are connected to the called user. This control method has a simple mechanism, but the networking is not flexible. For example, a step-by-step switch can only use the incoming call tandem mode.

1.2 Indirect centralized control

Also called indirect public control. Based on the address information, after analysis, control the switching logic and send the address and additional information to the next switch. This control method has strong control functions, flexible networking, high network utilization, and can use common channel signaling. According to the implementation method of control logic, indirect centralized control can be divided into three types: manual control, wiring logic control and stored program control.

Manual control

Regardless of circuit switching or message switching, control logic and switching logic are performed by professionals. In some aspects, it has great flexibility and adaptability (such as tracking and finding people, inquiries and transmissions, etc.). Although the manual control method is not suitable for services with large traffic volume and small call delay, as a subnet of an automatic network, it still has its special purpose.

Wiring logic control

The control logic is realized by the action of the functional parts and the wiring connection between them. The signaling channel and the communication channel are completely separated in the machine. It is suitable for switches with hierarchical contact arrays and circuit switching logic (such as crossbar switches).

3. Stored Program Control

The control logic is stored in the memory of the computer in the form of a program, and the address and network status information are used as input data. The computer calls the program for analysis and processing, and converts it into a driving signal to perform control. Because the program can be rewritten and adjusted, it has great flexibility. It can be used for switches of various types of switching logic, and can perform flow control and network management according to the characteristics of the switching logic.

Program-controlled air separation switch. Stored programs are used to replace wiring logic to achieve the same control functions as the horizontal and vertical indirect centralized control (such as program-controlled semi-electronic switches and program-controlled air separation electronic switches).

Program-controlled time division switch. The address information is provided by channel signaling or common channel signaling, and the retransmission circuit switching logic is periodically stored in units of time slots, that is, circuit switching between time division multiplexing systems is realized by time slot switching and time division space division switching. The stored program is mainly used for the logic control of the memory write and read delay and the array switching of the cross-point switch array. The time slot exchange delay is less than the frame period and can be used for real-time interactive communications, such as program-controlled digital telephone switches.

Program-controlled message switch. The header is exchanged and transmitted with the message, in principle, a message is used as the unit. The switch program is mainly used to determine the logical control of the route. The circuit utilization of this switching method is high, but the delay is large.

packet switch. At the sending end, the data to be sent is divided into equal-length packets. Before each packet, a flag item carrying information such as address and packet serial number is added, and sent together with the data packet. The program of the switch is mainly used to analyze the logical control of the received packet flag items, routing, error checking and flow control. The relay circuit of the packet switch has high utilization rate and small delay, which is suitable for small burst data transmission and interactive communication.