1,2 Using Methods: This 2 way voice intercom system has 2 using methods, you can press the green key to ring the other side or press and hold the key to speak directly, which is very easy to operate. 2,Compact And Lightweight: This 2 way intercomunicador door bell is small in size, light in weight and has a slim appearance with a thickness of only 18mm, making it very easy to install and use. 3,Built In 1800mAh Battery: This wireless intercomunicador has a built in 1800mAh battery in both the internal and external units, which can work for about 1 week with a normal working time of 5 times a day, 30 seconds at a time. 4,Long Transmission Distance: The transmission distance of this wireless intercom doorbell can reach up to 1000 meters in open areas and 20 to 50 meters through walls, which is practical and can be applied in most scenarios. 5,Good Workmanship: This electronic doorbell intercomunicador's buttons are made of plastic and silicone structure with high gloss UV process on the surface, super feel, rugged and not easy to be damaged. Item Type: 2 Way Voice Intercom System Material: ABS Battery: Inner Machine: Polymer Lithium Battery 3.7V 1800mAh x 1 (Included) Outer Machine: Polymer Lithium Battery 3.7V 1800mAh x 1 (Included) Battery Power Supply: DC5V or 1A Operating Temperature: -20°C-55°C Transmission Distance: Approx. 1000m or 3280.84ft in open space, 20-100m or 65.6-328.1ft through walls, 1-8 floors Working Frequency: 410-490MHz Working Time: Approx. 3 days on a single charge Charging Time: Approx. 5 hours to fully charge Music Ringtones: 38 Melodies Ringtone Volume: 3 Levels Sdjustable (Volume Adjustment Key in Standby Mode) Call Sound: 3 Levels Adjustable for Call Volume (Volume Adjustment Key During Calls) Size: Main Machine of Doorphone and Indoor Intercom: Approx. 116 x 56 x 18mm or 4.57 x 2.2 x 0.71in Waterproof Cover Size: Approx. 121.5 x 61.5 x 31.3mm or 4.78 x 2.42 x 1.23in Charging Dock Size: Approx. 70 x 56 x 29mm or 2.76 x 2.2 x 1.14in 1 x Indoor Machine 1 x Outdoor Machine 1 x Base 1 x Data Cable 1 x Screwdriver 1 x Manual 1 x Double Sided Tape