A toroid can be used for multiple purposes, it is generally a ring shaped magnet. This toroid magnet can be used as an inductor in electronic circuits. The most common use of a toroid is in transformers. Transformers bring the voltage up and down in an electric circuit, and are used in most houses.
One of the most popular companies to buy a toroid from is Molex, they are a manufacturer of electronic systems. They have thousands of other products such as lighting and mobile devices. Another trusted company is Honeywell, they have various products including security alarm systems. They even have a Honeywell Security Group unit that focuses on burglar alarm systems, as well as fire alarms. Their systems are trusted by many residential homes and commercial businesses around the world.