Abstract
This paper is concerned with a radio telemetry system for the measurement of skin potential level (SPL). It is known that SPL reflects the level of vigilance under inactive state of body, such as sitting and lying. The fact may be applied to controlling sleepiness with the aid of the biofeedback technique. In order to clarify the relation between SPL and sleepiness and to test the possibility of its application, we made a compact telemeter device for SPL measurement, which was reported in the previous paper. In this study we improved it in size, weight, stability, and power consumption. We used FM-FM type modulation to make the transmission more stable. The weight of the transmitter is 90g and its size is as small as a cigarette case, which permits free movement of body in measuring SPL. Any commercial FM receiver can be used as a receiver of this system. Its output, I. e. audio signal, is demodulated into the original wave form of the SPL through a phase-locked-loop circuit. With the use of the system, SPL was measured under various conditions such as doing sports, whole-night sleep, and driving a car. The obsedved changes in SPL show that it can be regarded as a good index for the vigilance level under active state of body as well as under resting state.
