Extech 412440-S Calibration Source CheckerExtech 412440 S Current Loop Checker Current Loop Checker Low cost, pocket sized checker for simulating Current Loops Instantly determine if your device needs calbration Key Features: Simulates output ranges of 4mA, 12mA and 20mA from transmitter Ideal for checking calibration and as a current source for setting up engineering units on a process indicator or controller Bright red LEDs indicate simulation output or battery status Accurate to 0. 1mA