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 assign