Which statement correctly defines Plain Old Telephone Service in the context of alarm systems?

• A. Point Of Telemetry System
• B. Public Optical Transmission Service
• C. Plain Old Telephone Service
• D. Private Onsite Telecommunication Solution

Answer: (C)

Plain Old Telephone Service refers to the traditional landline service that connects to the public switched telephone network, usually via a copper two‑wire line. In alarm systems, this channel is used by the control panel’s dialer to call the monitoring center, sending signals the same way a voice call would travel. It’s the baseline, legacy option that many systems historically relied on, distinct from newer methods like optical/fiber, cellular, or private networks. It’s widely available and simple, but can be vulnerable to line cuts or service outages and is gradually being supplanted by newer communications methods.