Patent ID: 7671580

Claim:
An integrated current sensing circuit for sensing at least two test loop circuits, said integrated current sensing circuit comprising: a current sensing transformer including a first primary winding element, a second primary winding element and a secondary winding element, wherein a sensing current is outputted from said secondary winding element when either a first test current is inputted into said first primary winding element or a second test current is inputted into said second primary winding element, wherein in the case where said first test current is inputted into said first primary winding element, the ratio of said sensing current to said first test current is equal to a first value, and wherein in the case where said second test current is inputted into said second primary winding element, the ratio of said sensing current to said second test current is equal to a second value; and a rectifying circuit for rectifying said sensing current into a first measuring current or a second measuring current when said first test current or said second test current is sensed, wherein said rectifying circuit includes a first input end, a second input end, a first output end, a second output end and a common node, said first input end and said second input end are coupled to both terminals of said secondary winding element, said first measuring current is outputted from said first output end, and said second measuring current is outputted from said second output end, wherein in the case where said first test current is sensed, the ratio of said first measuring current to said first test current is equal to said first value, and wherein in the case where said second test current is sensed, the ratio of said second measuring current to said second test current is equal to said second value.