Xiaomi Solar Outdoor Camera BW400 Pro Set (camera + base station)

How many megapixels one lens records, per the manufacturer: more pixels show more detail when you zoom in — faces, number plates, small objects. The exact frame size in pixels is in the note; for multi-lens cameras this is the resolution of one lens, not the total.

A fixed camera always looks in one direction. A pan-tilt (PT) camera turns on command from the app, on a schedule or to follow a person, so one camera can cover a whole room or yard. Models with one fixed and one pan-tilt lens show a wide view and a moving view at the same time.

How many separate lenses, each with its own sensor, the camera has. Several lenses show different areas, or a wide and a close-up view, at the same time — each as its own picture in the app.

How much of the scene the lens takes in without turning. A wide angle shows more space but makes objects smaller; a narrow one shows less space but larger, more detailed objects. Horizontal and vertical angles, where published, are in the note; for multi-lens cameras this is the widest lens.

Infrared illumination is invisible to the eye and gives a black-and-white picture in total darkness. Colour night vision switches on a visible white light — the picture is in colour, but the light can be seen from outside. Cameras with very bright optics give colour under weak outside lighting without a light of their own. If both of the first two are listed, the camera switches between them, for example when it detects a person.

How far the camera's own illumination still lights the scene in the dark, per the manufacturer. Beyond that, objects are visible only with outside lighting. If different values are given for infrared and white light, they are in the note.

A microSD card stores recordings for free; in kits with an indoor unit it may sit in that unit rather than the doorbell, so recordings survive if the doorbell is taken off the door. Cloud storage keeps recordings on the maker's servers, usually with a paid subscription.

The largest card, in gigabytes, the device accepts. Whether a card is in the box is in the note.

Which events the device tells apart and sends separate alerts for, besides a button press. Person recognition filters out false alarms from cars and branches, and loitering tells you someone is standing at the door without ringing. Which sensor detects motion (PIR infrared or video analysis) is in the note.

Microphone only — the camera records sound with the video. Two-way audio — there is also a speaker, so you can talk through the app to whoever is in front of the camera.

Where the device gets its power: 230 V mains, an adapter, USB, batteries or a built-in battery.

The built-in battery’s rated capacity. Run time also depends on how the device is used.

Whether the camera's battery can be topped up from a solar panel, and whether one is in the box. A panel keeps the camera running without taking it down, but in cloudy winter months it may not produce enough. The panel's power rating is in the note.

The supply voltage (and current, if stated) as the maker gives it. It must match your mains or adapter.

How much power the device draws on its own while idle. It matters for devices that run around the clock.

The wireless link or network the device uses. Wi-Fi connects straight to the router; Zigbee, Thread and Bluetooth Mesh work through a hub or gateway.

Whether the device needs a separate hub, gateway or coordinator to work in a smart home. If so, it is sold separately unless stated otherwise.

The maker’s app used to set up and control the device.

Protection against dust (first digit) and water (second). IP20 is for dry rooms only, IP44 resists splashes, IP65 and up handle water jets and outdoor use.

How and where it is installed: in a wall box, on a wall or ceiling, on a DIN rail, on a table or in a socket.

The air temperature range the device is rated for. The lower limit matters outdoors, on balconies and in unheated rooms.

What comes in the box, per the maker.