With flash LED, classical streamline artwork, simple and elegantStrong digital anti-interferenceSpecial design for people who has hearing impairedTwo tones optional: Ding Dong/Golden MelodyBattery requirement:Transmitter: 12V/23A alkaline batteryReceiver: 3 x 1.5V AA alkaline batteryOperating range up to 100m (no obstacles)Frequency: 315/433MHz +/- 0.5 MHzMinimum order quantity: 2,000 pieces