The Circuit Buddy LED test light consists of red and green LED's to indicate voltage and polarity and will not cause damage to sensitive electronics. The test light is rated 6 to 48 Volt although the LED's become visible at just below 4 Volt, intensity will increase as the voltage increase up to 50 Volt MAX. LED's responds instantly and able to indicate pulses e.g. automotive injector supply pulses. The approximate current drawn by the LED circuit tester are as follows: 1.85 mA @ 6 Volt, 3.7mA @ 12 Volt, 7.4 mA @ 24 Volt and 14.8 mA @ 48 Volt.