A printing unit having a tucker bar capable of tucking a tail edge of a printing plate into an axially-extending gap of a plate cylinder and a tucker bar control device for automatically moving the tucker bar from an operating position to a non-operating position so as to permit access to the axially-extending gap. At least eight sequentially positioned elongate contact members are connected in a series of signal pairs. Some of the specific applications include the monitoring of ECG, EEG, EMG, glucose, electrolytes, body hydration, dehydration, tissue state and wounds.