A coupling interface for establishing an electrical connection with an electrically conductive article coupled across an arbitrary pair of conductive regions (311, 312, 313, 314), said interface being adapted to: establish in a first state a potential difference of a first polarity between a first said conductive region and a second conductive region, measure a characteristic of an electrical property between said first conductive region and said second conductive region in said first state, determine that said characteristic falls within a predetermined range, and characterised by being further adapted to: establish in a second state a potential difference of a second polarity between the first said conductive region and the second conductive region, said second polarity being opposite said first polarity, measure a characteristic of an electrical property between said first conductive region and said second conductive region in said second state, determine whether said characteristic of an electrical property between said first conductive region and said second conductive region in said first state differs in a predetermined manner from said characteristic of an electrical property between said first conductive region and said second conductive region in said second state, and in a case where said characteristic of an electrical property between said first conductive region and said second conductive region in said first state differs in a predetermined manner from said characteristic of an electrical property between said first conductive region and said second conductive region in said second state,said interface being further adapted to establish the respective persistent electrical connections to said first conductive region and said second conductive region by said switching operation accordingly. establish in a first state a potential difference of a first polarity between a first said conductive region and a second conductive region, measure a characteristic of an electrical property between said first conductive region and said second conductive region in said first state, determine that said characteristic falls within a predetermined range, and characterised by being further adapted to: establish in a second state a potential difference of a second polarity between the first said conductive region and the second conductive region, said second polarity being opposite said first polarity, measure a characteristic of an electrical property between said first conductive region and said second conductive region in said second state, determine whether said characteristic of an electrical property between said first conductive region and said second conductive region in said first state differs in a predetermined manner from said characteristic of an electrical property between said first conductive region and said second conductive region in said second state, and in a case where said characteristic of an electrical property between said first conductive region and said second conductive region in said first state differs in a predetermined manner from said characteristic of an electrical property between said first conductive region and said second conductive region in said second state,said interface being further adapted to establish the respective persistent electrical connections to said first conductive region and said second conductive region by said switching operation accordingly. establish in a second state a potential difference of a second polarity between the first said conductive region and the second conductive region, said second polarity being opposite said first polarity, measure a characteristic of an electrical property between said first conductive region and said second conductive region in said second state, determine whether said characteristic of an electrical property between said first conductive region and said second conductive region in said first state differs in a predetermined manner from said characteristic of an electrical property between said first conductive region and said second conductive region in said second state, and in a case where said characteristic of an electrical property between said first conductive region and said second conductive region in said first state differs in a predetermined manner from said characteristic of an electrical property between said first conductive region and said second conductive region in said second state,said interface being further adapted to establish the respective persistent electrical connections to said first conductive region and said second conductive region by said switching operation accordingly.