Abstract: A low power consumption switch interface circuit (100) includes a current source (109) for providing switch current (144) having a magnitude dependent on a state of a current range signal (135). An input terminal (142) is provided to conduct the switch current (144) to an external switch (102). A circuit (101, 103, 119) for detecting a signal (141) present at the input terminal (142) provides a measured pulse (127) when the signal (141) is detected. A current range selector (129), coupled to the current source (109), outputs a first state of the current range signal (135) while the measured pulse (127) is outputted from the circuit (101, 103, 119), and a second state of the current range signal (135) while the measured pulse (127) is not outputted from the circuit (101, 103, 119).