Sonoff 4CH R3/ 4CH PRO R3 4 Gang Wi-Fi Smart Switch Module Voice Control Interlock Inching Control via eWeLink APP Support Alexa SONOFF 4CHR3 & 4CHPROR3 are both 4-gang DIY Wi-Fi Smart Switches designed to give you the ability to integrate smart control into your existing home to enable a smart home. Each smart switch has 4 gangs that can be used to control lights and other home appliances at the same time in four areas of your home. There is a major difference between 4CHR3 and 4CHPROR3, which is 4CHPROR3 is designed with an additional function for RF control. The function is purposely adopted to make you turn on/off the device connected with 4CHPROR3 via the SONOFF RM433 remote controller.Actually, SONOFF has ever released two types of 4-gang smart switch (4CHR2 and 4CHPROR2) which comes with almost same functions with 4CHR3 and 4CHPROR3. But all the above units are still different in 3 working modes including self-locking, interlock and inching mode. The new improvement on 4CHR3 and 4CHPROR3 compared with 4CHPR2 and 4CHPROR2 is for users to set these 3 working modes on eWeLink APP instead of the hardware itself, easier to operate. So you can enable self-locking mode to turn on/off 4 connected devices separately, interlock mode to turn on 1 connected device every time and turn off the rest of devices simultaneously and inching mode to turn on 1 connected device and then make it turn off automatically after a given time (0.5 - 3600s). For the device away from the switch, you can create a moveable space in virtue of a DIN rail to make them be connected. Simply activate devices through your voice when the switch works with Alexa and Google Home smart assistant. Quick to Access 3 Working Modes Compared with 4CHPROR2, you can access self-locking interlock and inching mode on APP directly. Run 4 Devices Separately- Self-locking Mode Allow you to turn on or off 4 connected lights independently.