A power supply control device comprising a controller, a probing signal source, a load monitor and power connection circuitry operable by the controller, wherein the power connection circuitry comprises a switchable power connection path (P1, P2) between a source side and a load side, and the power connection path is switchable to operate in a first operation state which is an on-state to permit flow of operation current through the power connection path, or a second operation state which is an off-state to impede flow of operation current through the power connection path; characterized in that, - the controller is to operate to make identification and electrical characteristics enquiries by sending enquiry signals to the load side and to determine with reference to received responsive signals, which are responsive signals received from the load side, whether a load on the load side is an admissible load eligible for power supply connection; - wherein if the received responsive signals to the identification enquiry contain identification data of an admissible load, and - if the received responsive signals to the electrical characteristics enquiry contain electrical characteristics matching with or corresponding to stored reference electrical characteristics data of the admissible load, the controller is to switch the power connection path to the on-state or to maintain the power connection path to the on-state; - wherein the controller is to make the identification enquiry and to receive identification enquiry responsive signals, which are responsive signals received in response to the identification enquiry, by way of protocol communication via a communication interface (COM 1, COM 2) of the controller; - wherein the controller is to make the electrical characteristics enquiry by operating the probing signal source to send probing signals to the load side, to collect and measure responsive signals received at the load monitor, to evaluate and obtain responsive electrical characteristics of the load using the collected responsive signals, and to determine whether the responsive electrical characteristics match with or are in correspondence with stored reference electrical characteristics of the admissible load; and wherein the probing signals include one or more of: AC voltage of variable frequencies and constant or variable amplitudes, AC voltage of a constant frequency and variable amplitudes; pulse signals or trains, of specific or variable periods and of constant amplitude or variable amplitudes; step signals, of variable rise times and of constant amplitude or variable amplitudes. - the controller is to operate to make identification and electrical characteristics enquiries by sending enquiry signals to the load side and to determine with reference to received responsive signals, which are responsive signals received from the load side, whether a load on the load side is an admissible load eligible for power supply connection; - wherein if the received responsive signals to the identification enquiry contain identification data of an admissible load, and - if the received responsive signals to the electrical characteristics enquiry contain electrical characteristics matching with or corresponding to stored reference electrical characteristics data of the admissible load, the controller is to switch the power connection path to the on-state or to maintain the power connection path to the on-state; - wherein the controller is to make the identification enquiry and to receive identification enquiry responsive signals, which are responsive signals received in response to the identification enquiry, by way of protocol communication via a communication interface (COM 1, COM 2) of the controller; - wherein the controller is to make the electrical characteristics enquiry by operating the probing signal source to send probing signals to the load side, to collect and measure responsive signals received at the load monitor, to evaluate and obtain responsive electrical characteristics of the load using the collected responsive signals, and to determine whether the responsive electrical characteristics match with or are in correspondence with stored reference electrical characteristics of the admissible load; and wherein the probing signals include one or more of: AC voltage of variable frequencies and constant or variable amplitudes, AC voltage of a constant frequency and variable amplitudes; pulse signals or trains, of specific or variable periods and of constant amplitude or variable amplitudes; step signals, of variable rise times and of constant amplitude or variable amplitudes.