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What is the working principle and function of a telephone switch?

📅Aug 11, 2026

Telephone Switch Principle In fact, the basic principle of a telephone switch is quite simple: it is the concentration and switching of voice. The main task of a telephone switch is to establish conne

What is the working principle and function of a telephone switch?

Telephone Switch Principle

In fact, the basic principle of a telephone switch is quite simple: it is the concentration and switching of voice. The main task of a telephone switch is to establish connections for calls between users, which is basically divided into two major parts: the speech path equipment and the control equipment. The speech path equipment mainly includes various interface circuits (such as subscriber line interface circuits and trunk line interface circuits, etc.) and the switching (or connection) network. The control equipment in a crossbar switch mainly includes markers and registers, while in a program-controlled switch, the control equipment is an electronic computer, including the central processing unit (CPU), memory, and input/output devices. A program-controlled switch is essentially a switch that uses a computer for "stored program control." It compiles various control functions and methods into programs, stores them in memory, and uses scanned data of external states and stored programs to control and manage the operation of the entire switching system.

Program-Controlled Telephone Switch Functions

  1. Providing IP telephony service functions, specifically including IP prefix addition, IP permissions, IP billing, and IP networking.

  2. IP prefix addition function: Based on actual usage, the system can automatically add the outgoing trunk prefix and the carrier access number.

  3. IP permissions: The system is configured with four IP permission levels: IP International 1, International 2, Domestic 1, and Domestic 2.

  4. IP billing: The system provides flexible IP billing functions. According to the current IP tariff standards and billing methods, IP call rates, discount methods, whether to charge local call fees, and which type of local call fees to charge can be flexibly configured.

  5. IP networking: Using IP telephony to implement networking.

Basic Functions of a Telephone Switch

  1. Internal calls: No telephone charges required.

  2. Flexible numbering: Arbitrary number assignment.

  3. Incoming external calls: Direct connection to extensions, with call transfer between extensions.

  4. PC-based traffic monitoring and management: Real-time billing for outgoing calls, clear at a glance.

  5. Class-based call restriction: Local calls and long-distance calls can be freely enabled or restricted.