Description :  KERUI D021 Wireless Garage Magnetic Door Sensor Shutter Door Alarm 433MHz with Alloy Roller Rolling Gate Reed Switch   Features :   This set includes magnets and wireless transmitter.  When the rolling door is open、 the transmitter will send wireless signal to the control panel. Used for the shutter doors or gates.  It sends out alarm signal when its magnetic strip is separated from the base (reed switch). Manufactured by the alloy materials、 waterproof and anti-rust. Alloy housing、 stainless threaded pipe、 reed switch.    Specification :  Action distance: 45-60mm Work Frequency: 433MHz Power supply: 12V 23A battery (Battery Includes.) Emission distance: 300 - 600 feet in open areas Contact resistance: <200mΩ Work Environment Temperature: -10 to +50\u2103 Humidity: ≤90% Chip Number: 1527、 smart study encoding、 not fixed code. Switch form: Normal Open (NO) or Normal Closed (NC)   Package includeds :  1 x KERUI Magnetic Door Sensor 1 x KERUI Reed Switch 1 x KERUI Emitter  Details pictures :