Businesses in the burglar alarms and security systems category supply, install and maintain equipment designed to protect homes and commercial premises against unauthorised entry. Systems may include wired or wireless intruder alarms, door and window contacts, motion detectors, control panels, internal and external sirens, and panic buttons. Installers can assess a property, recommend suitable equipment and configure it to match the layout and the customer's security requirements. Other services may include CCTV cameras and recording equipment, video doorbells, intercoms, access-control systems and connections to alarm-receiving centres for monitoring. Businesses commonly provide fault diagnosis, repairs, battery replacement, system upgrades and routine servicing, as well as guidance on using the equipment. Some supply components for customers to fit themselves, while others handle installation and set-up. The exact range of products and services varies between providers.