Preparation for transmission and reception of electrical signals

The invention provides a convenient and non-invasive means to prepare cells, tissues, and organs for electrical transmission and reception. In an embodiment of the invention, a control method comprises the use of at least one skin electrode, as a reference electrode, and an electrical sensor to measure periodically or continuously the skin's electrical conductance at the site of preparation. The dynamic change in the conductance through the skin is measured while the ultrasound is applied. Signal processing is performed on the measurement and the level of skin impedance change is controlled by performing a mathematical analysis and using the results of such analysis to control the application of ultrasonic energy. A desired level of skin impedance can be set at a predetermined value or based on a chosen level of skin integrity, subject's sensation of discomfort, or duration of the ultrasound application.