Wireless transmission, easy installation, ready to use after delivery. Adopt waterproof design to avoid corrosion from tea, oil and water during work. Built-in 300mAh large-capacity lithium battery, capable of 37 hours of standby. Super resistant and anti-fall. All internal circuits are reinforced and more stable against drops.Can be used with 16 receivers, no need to worry about insufficient occasions. Adaptive power supply: DC 12V/1A Charging current: 20-50mA Standby time: 200 hours Number of code pairing: 998 Prompt mode: buzzer/vibration/light Modulation mode: AM OOK Working frequency: 433.92MHZ Menu option:set prompt time:set buzzer speed Set base ID/set extension number:set switch vibration Transmission distance: 800 meters in open space Voltage:AC220V Plug Type:EU Plug,it applies to Indonesia, Germany, France, Spain, Italy and so on Note:Due to different production batches, there may be slight differences in products. Colour:Black Material:ABS Package Contents: 1 x Wireless Calling System 16 x Receiver Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm. Note: 1. Please allow 1-3 mm error due to manual measurement and 1-3g weight error make sure you don't mind before ordering. 2. Due to the lighting of the photos and the difference of monitors, the pictures may not reflect the actual color of the real item. Please make sure you don't mind before ordering, thank you! About Shipping: 1.please pay attention to your delivery address such as: name, street, house number, doorbell/email without name, etc. is correct, or the order will not be delivered correctly. 2.All items will be shipped within 3 business days after the payment is received. Most times you will receive them within 8-12 days then. The specific delivery time is depend on circumstances. 3.During the shopping process, if you have any questions, please feel free to consult us, we will reply you within 192 hours Hope you have a pleasant shopping experience!