There is a 4-wire system connection. Use a 4-core cable to connect the outdoor camera and monitor. The maximum distance can reach 100 meters. Different distances and cables of different diameters are used. Please check the following to select the corresponding cable. When a visitor ring , the monitor will be activated and show the image outside. Press the answer button, then you can talk to outside, press the answer button again to turn it off. If you do not press the button after conversation is finished or if answer the call, the monitor will turn off automatically after 60s. The 25 polyphonic ringtones can be switched freely, which is elegant and beautiful. The ringtone and volume can be adjusted to meet your needs. No longer have to worry about not being to hear the sound or hearing the sound too loud. This video intercom can connect to the electric lock. You can open the door with both the indoor monitor and outdoor camera. Very convenient! ( Note: locks are NOT including in the package, need to buy extra) The NO type lock can be connected to the camera directly. But the magnetic lock, Strike lock and need to be connected to an extra DC12V power supply Camera sensor 1/4inch CMOS Lens Angle 92 degree Night Vision IR light Electronic lock support Power Consumption 200mA Max. Material aluminium alloy panel Waterproof IP65 Operation Temp. -40 degc +50 degc Installation Wall mounted The Outdoor Camera Is Equipped With Rubber Gasket Ring, There Is No Way To Leak. It Also Can Works Well Even In Bad Weather. 1.0MP High Resolution,It's See And More Details Than 1200TVL/800TVL. The LED on the outdoor doorbell will light on automatically so that you can see clearly of visitors even in the darkness of evening , Make sure your family is safe. Plug Type :EU Plug,it applies to onesia, Germany, France, Spain, Italy and so on. Colour:As Shown Material:plastic+metal Voltage: AC100-240V Package Contents: 1 x Video Doorbell Door System Kits 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.