Bell 500LX is a door entry system that allows for two-way communication between a visitor at the door and a resident inside the building. It consists of an entrance panel with a microphone and speaker, and one or more indoor telephones. The system can be expanded to include additional telephones, door entry panels, and other devices such as electric door releases and time clocks.

The Bell 500LX is easy to install and use. The entrance panel is typically mounted on the outside of a building, near the front door. The indoor telephones are mounted in convenient locations inside the building. The system is wired together using standard telephone cable.