The Public Switched Telephone Network is the traditional circuit-switched telephone network. It has carried voice calls for over a century. It uses copper wires, fiber, microwave, and satellites. It connects homes and businesses to central offices. It is the phone network that Alexander Graham Bell would recognize.

PSTN is circuit-switched. A dedicated path opens for each call. It stays open until the call ends. The network is reliable and low-latency. It works during power outages if the line is powered by the central office. It is also expensive to maintain and inefficient.

PSTN characteristics

• Circuit-switched: dedicated path
• Reliable: works in power outages
• Low latency: no packet delays
• Declining: replaced by VoIP and mobile
• Legacy: copper network aging

PSTN is being phased out. Telecom companies are moving to VoIP and fiber. The copper network is expensive to maintain. Regulators are allowing retirement. But some people still rely on it. Rural areas, older adults, and alarm systems. The PSTN is a legacy. It served well. Its time is ending.