The AlertMaster AMBX Baby Monitor, by Clarity, is a signaling transmitter that provides notification to a childs cries. It becomes activated after five seconds of sound and is an ideal solution for parents and those with a moderate-to-severe hearing loss. Nine-volt battery included. The AMBX is an optional accessory to the AM6000 Notification System; a receiver is required. What else do I need to make this work? In order to be notified, you will need to purchase a receiver that lets you know when the signaler or transmitter is activated (see Related Products box).