an electronic circuit arranged to terminate automatically a plurality of conductors at or near a node of a network comprising : a first input terminal electrically coupled to a first output terminal ; a second input terminal electrically coupled to a second output terminal ; selectable current limiting means arranged to limit an amount of current that may flow between the second output terminal and the second input terminal ; and detecting means arranged to control switching means operable to switch the circuit between a first and a second condition responsive to the electrical potential vx of the second output terminal , wherein in the first condition the circuit is a terminating circuit and the sclm is selected to have a first current limit , and in the second condition the circuit is a continuing circuit and the sclm is selected to have a second current limit .