This app allows you to control a 2, 4 or 8 Channel Relay Module Bluetooth BLE with your smartphone. To use this app, you need one of these three modules: "2 Channel Relay Module Bluetooth BLE" "4 Channel Relay Module Bluetooth BLE" "8 Channel Relay Module Bluetooth BLE" These modules can be ordered at many online shops. Please use a search engine to find a shop. This app can be connected with any number of modules. By entering an alias, the modules are marked clearly and can easily be assigned to a use area. Name the modules for example "Relay 1", "Relay 2", "Electronic lab project" or "Ambient Light". An alias can also be entered for each relay. The default password for these modules is usually "12345678". For more security, the app also allows you to change the password. The password must be eight digits long.