The Microwave Receiver uses a plate antenna which gives high sensitivity over a broad area. The output is to an internal loudspeaker and power is derived from a mains plug-top unit (supplied). A control allows the user to adjust the sensitivity to cater for different circumstances and distances.Additional parts available:Microwave Transmitter Unit: B8R09403Microwave Probe Receiver: B8R09450Microwave Accessories: B8J73480Full Microwave Kit with Accessories: PP053304