Additional Features: Clear plastic cover is provided for safe measurements. Opening the cover decreases the voltage generated by back-e.m.f. (electromotive force) to a level below 40 V within 0.1 second. Heat-sensitive switch prevents DUT from overheating. Also equipped with DC bias voltage monitoring. The Agilent 42842A is designed for use with the Agilent 42841A. It is connected directly to the bias current output terminals of the Agilent 42841A.