Module A-175 (Dual Voltage Inverter) is exactly what it says it is: two identical inverters, which will take a voltage and output it in an inverted form - so that an input of +5 V will be output as -5 V, an input of -2 V will be output as +2 V, and so on. 
Two LEDs give a visual indication of the (positive or negative) output signal.

For more detailed information please look at the English user's guide: A175_man.pdf