The icons for cellular signal strength, remaining battery, Bluetooth connection, and Wi-Fi connection are common cellphone icons. Although these icons indicate the same information in general, their exact meanings may differ from one cellphone operating system to another.
The cellular signal strength icon is generally four or five bars next to one another. The bars get taller from left to right. The better the connection to a cellular station, the more bars the cellphone fills. When the icon turns into an empty-set symbol, it means there is no signal and the phone is not connected to a network.
The battery icon indicates the phone's remaining battery power. Depending on the platform, the icon may have a charger icon or a lightning bolt symbol on top of it when the phone is charging. When the icon is empty, the phone is out of power and shuts down. Some cellphones disable various features automatically when the battery is nearly empty to preserve energy.
The Bluetooth and the Wi-Fi icons indicate whether or not the phone is connected to a Bluetooth device or a Wi-Fi network. Similarly to the cellular signal strength icon, the Wi-Fi icon can also indicate the signal strength. Note that the Wi-Fi icon does not indicate an Internet connection. Depending on the network, users may be unable to connect to the Internet even with a full Wi-Fi icon.