Patient Pager System 20Pcs Waterproof Call Buttons Adjustable Volume Stable Wireless Wireless Calling System 110‑240V US Plug Item Type: Patient Pager System Material: ABS Display Receiver Parameters: Operating Frequency: 433.92MHz Operating Current: <130mA Standby Current; <550mA Modulation Mode: ASK Receiving Sensitivity: Better Than -105dB Decode: Study Code Waterproof Grade: IPX4 Operating Temperature: Minus 20℃ to 60℃ Button Transmitter Parameters: Operating Frequency: 433.92MHz Alkaline Battery Model: 12V23A (Included) Battery Capacity: 30mAh Transmitting Current: 10mA±3mA Standby Current: <1uA Open Space Distance: >200 Meters / 218.7yd Keys: A Million Times Waterproof Grade: IPX7 Operating Temperature: Minus 20℃ to 55℃ Single Button: Call