The KTA-366 is a 4-20mA loop powered current calibrator suitable for testing 2 and 3 wire transducers. Contains a three position rotary switch, that selects between these operations: 4 mA – used to inject 4 mA into the loop. ADJ – used in conjunction with the potentiometer to select 4 mA, 20mA or any value in between. 20 mA – used to inject 20mA into the loop. Two operating modes: Simulate mode: Simulates 2-wire, loop-powered transducer. This mode uses an existing power supply or excitation connection on the PLC/DAQ equipment. Generate mode: Generates a 4-20mA powered signal that can drive the input on a PLC/DAQ. In this mode, the KTA-366 is more like a 3-wire transducer or a signal conditioner. This mode requires power to be fed to the KTA-366 via its DC power jack. See related products for a suitable plug pack. Datasheet - http://www.electronics123.net/amazon/datasheet/KTA-366Manual.pdf