Applying electrical stimulus to a system and aquiring the system response

The present invention relates to a device and apparatus for applying electrical stimulus to a system and acquiring a system response, particularly in clinical environments. According to the present invention there is provided use, in the detection of medical conditions, of a portable test device for generating an electrical signal to be applied to a system and acquiring a response signal generated by the system, the device comprising signal generation means, signal receiving means, and signal processing means, wherein, in use, the device generates a signal to be applied to a system to be tested and receives a response signal of the system which was tested whereby the applied and received signals undergo processing by the signal processing means, providing data representative of a characteristic of the system. The invention may be used for portable wireless of physiological properties. The apparatus is battery powered and may display the processed data. In particular the apparatus detects electrical properties of parts of a body and may be used in the detection of dental caries or skin conductivity.