The GSR100C measures both the skin conductance level (SCL) and response (SCR) as they vary with sweat gland (eccrine) activity due to stress, arousal or emotional excitement. The GSR100C uses a constant voltage technique to measure skin conductance. The controls allow selection of absolute (SCL+SCR) or relative (SCR) skin conductance measurements. Each GSR100C amplifier requires one TSD203 electrodermal response transducer. For alternative body placement, use two of the EL258 lead electrodes (instead of the TSD203) with the GSR100C. Also required is GEL101 electrode gel or your preferred isotonic recording gel.