A method and apparatus for obtaining signals from the anode buses of a mercury cell to provide automatic protection against short circuits, visual readouts, and computer information. A multiplexer is associated with each cell which scans the signals from the various bus bars. The scanned signals from each bus bar are sequential with one another and are converted to proportional voltage and anode bus current signals, which are transmitted to a console for decoding and processing to provide a visual readout and to a computer for processing and anode adjustment. In addition, each cell has an overcurrent and short circuit protection circuit based upon anode bus current. The instantaneous anode bus current for a given bus of a cell is compared with an average anode bus current for that cell and the anodes raised when the current exceeds the average bus current by a certain percentage.