A method of detecting possible living body contact at an electrical contact surface, wherein the living body has a detectable characteristic initial impedance and a corresponding characteristic time constant defined by the initial impedance upon touching the electrical contact surface when the electrical contact surface is at a touching voltage, wherein the method comprises sending a non-hazardous probing signal to the contact surface, wherein the probing signal comprises one probing pulse or a plurality of probing pulses forming a probing pulse train, and the probing pulse has a base voltage level and a probing voltage level which is above the base voltage level and equal to the touching voltage or a probing voltage level which is below the base voltage level and equal to the touching voltage； detecting an electrical response from the contact surface in response to the electrical probing signal, wherein the electrical response comprises electrical response signals； and determining from the electrical response signals whether there is possible living body contact at the electrical contact surface.
