WiFi Power Meter SONOFF SPM-4 Relay Linkable Slave Unit  is a meter that can be used to keep track of consumption in different rooms, electrical components or household appliances, linking several points under a single display on the Smartphone, making it possible to monitor consumption, as well as its intelligent remote control. Features of the WiFi Power Meter SONOFF SPM-4 Relay Linkable Slave Unit Both the SPM - Main Master Unit and its slave unit SPM-4 Relay have a standard size allowing it to be placed on a DIN Rail. Pairing instructions with the eWeLink application: 1. Download the "eWeLink" app from APP Store for iOS or Google Play for Android. 2. Press the button for 5 seconds until the LED indicator flashes rapidly. Choose the appropriate pairing mode 3. The device will be automatically searched for and connected. 4. Enter the ID and password of the home Wi-Fi network. Applications of the WiFi Power Meter SONOFF SPM-4 Relay Linkable Slave Unit It is the ideal solution for