CCTV (closed-circuit television) is a television system in which signals are transmitted from cameras to monitors using a closed circuit, meaning that the signal is not publicly distributed. CCTV is often used for security and surveillance purposes, as it allows people to monitor a specific area or location from a central location. CCTV systems typically consist of cameras, monitors, and a recording device, and may be used in a variety of settings including homes, businesses, and public spaces.

A video door phone, also known as a video doorbell or door intercom,The system typically consists of a camera mounted at the front door and a display screen or intercom inside the building. When a visitor rings the doorbell, the camera sends a live video feed to the display screen, allowing the resident or employee to see and talk to the visitor.

A PA (public address) system is a sound amplification and distribution system that is used to amplify and broadcast audio to a large area or group of people. PA systems are commonly used in a variety of settings, including schools, churches, public buildings, and outdoor events. PA systems typically consist of a microphone, an amplifier, and one or more speakers. The microphone captures the audio signal, the amplifier increases the volume of the signal, and the speakers broadcast the amplified