SONOFF MINI Extreme Wi-Fi Smart Switch MINIR4 【Super Tiny Size】Its compact size allows it to be installed in various mounting boxes, including the smallest European standard. 【External Switch Control】Easily connect to the momentary switch, door exit switch, SPDT switch, latching switch, and even dry contact sensors. 【Detach Relay Mode】MINIR4 has “detach relay” mode, which means the states of external switches and relay are separated, so operating the external switch button won’t affect the relay state. .