Abstract: A personnel identification system for controlling access to restricted equipment or restricted areas comprises a portable device such as a wrist watch (10) in which a unique digital identification code is stored, and a static control unit having a conductive touch element (12) and a code signal receiver (14) for comparing the identification code with a stored access code. The watch (10) includes a transmitter for transmitting the identification code as a modulated alternating signal by electrical conduction through the wearer's body to the touch element (12), so as to provide resistance to interfering radiated signals.