Servo tester can be used to test the servo and ESC, connected to the ESC can give the motor speed. Comes with a voltage reduction circuit, can be directly connected to the 2S 3S 4S 5S 6S battery (5-26V), do not need external BEC wiring simple. If the servo tester needs to be connected to a 1S battery should be connected to a boost module, this link has a matching boost module to buy, module parameters, please check the content page, the module default output voltage is set to 5V