Feature: 1. Portable Doorbell Unit: This package includes 4 doorbell system units, 2 indoor and 2 outdoor, which can be switched between ringtone call and intercom mode. 2. Intuitive Indicator Lights: The system features a humanized design with intercom and power indicator lights, providing users with clear visual cues. 3. Long Transfer Range: The intercom system boasts an impressive transfer distance, reaching 1000 meters in open areas, and 20‑50 meters through walls, offering high practicality. 4. Adjustable Functionality: This portable intercom system comes with 2 channels, A and B, and 3 volume levels, allowing users to customize settings according to their preferences. 5. Reliable and Long Lasting: Stay connected with a single charge lasting up to 48 hours, ensuring continuous use with only one charge every two days. 6. Versatile Application: This clear sound intercom system is widely applicable to various scenarios, including hospitals, hotels, factories, teahouses, and more. Specification: Item Type: Wireless Intercom System Material: ABS Waterproof Level: IP54 Battery: Indoor Unit: Rechargeable Lithium Battery 3.7V 1800mAh x 1 (Shipped with Built in Battery) Outdoor Unit: Rechargeable Lithium Battery 3.7V 1800mAh x 1 (Shipped with Built in Battery) Application: Widely used in home, office, laboratory environment, hospitals, etc. Basic Parameters: Working Temperature: -20℃-55℃ Transmission Distance: Open space 1000m, through wall 20-50m Working Frequency: 410M - 490M Sound Adjustment: Three levels adjustable. Package List: 2 x Indoor Unit 2 x Outdoor Unit 2 x Base 2 x Data Cable 2 x DC Power Cable 1 x User Manual 1 x Sticker 1 x Screwdriver