In conducting tests we noticed that the Sonoff Basic R4 Wi-Fi Switch rated to operate at 100- 250v ac 50/60 Hz will actually operate with much lower input voltages. We tested the device with input voltages of 20v ac rms at 50Hz and 12v dc. In both tests the the device functioned reliably and as expected the voltage appearing at the output terminals when the relay was energised was the same as the voltage condition applied to the input terminals. The device also runs cooler with lower input voltages, This adds to the versatility of the device particularly in low- voltage applications.