Wireless Intercom Doorbell Two Way Voice Intercom System for Home Elederly Hospital Patient Nurse Item Type: Wireless Intercom DoorbellMaterial: Abs Battery Type: Polymer Lithium Battery Battery Model: 103450 Battery Capacity: 1800 Mah Power Supply: Polymer Lithium Battery (Delivered with Built-In Battery) Battery Powered: Dc5v/1a Operating Temperature: -20 Degrees Celsius~ 55 Degrees CelsiusTransmission Distance: About 1000 Meters Open, 20-100 Meters Partition Wall, Floor 1 ~ 8 Floor Operating Frequency: B Gear Frequency 462mhz a Gear Frequency 434mhz Working Time: Charge for About 1 Week Charge Time: About 5 Hours Full Music Ringtone: 38 Ringtones Ring Volume: 3 Levels of Adjustment (To Adjust the Volume of the Machine) Call Sound: Level 3 Adjust Call Level (Adjust Volume Button When Talking)