Abstract: A controlled, symmetrical, stable current source that can power floating resistive loads, eliminates the need to connect the load directly to either a power supply or ground and protects the load against overpower should either or both sides of the load be shorted to ground. The current source includes two operational amplifiers for providing a current through the load that is proportional to an input voltage applied across the respective non-inverting inputs of the two operational amplifiers; two current sensing resistors for providing voltage drops that are proportional to the current through the load; and four summing resistors connected to the sensing resistors for providing to the inverting inputs of the operational amplifiers voltages that offset the sum of the voltage drops provided by the sensing resistors so that the current through the load is controlled by only the input voltage.

Abstract: A controlled, symmetrical, stable current source that can power floating resistive loads, eliminates the need to connect the load directly to either a power supply or ground and protects the load against overpower should either or both sides of the load be shorted to ground. The current source includes two operational amplifiers for providing a current through the load that is proportional to an input voltage applied across the respective non-inverting inputs of the two operational amplifiers; two current sensing resistors for providing voltage drops that are proportional to the current through the load; and four summing resistors connected to the sensing resistors for providing to the inverting inputs of the operational amplifiers voltages that offset the sum of the voltage drops provided by the sensing resistors so that the current through the load is controlled by only the input voltage.

Abstract: A system and method of authentication electronic transactions in which personal hand writing patterns like signatures are used. Signatures are conveyed from sender to receiver through a data communications channel and stored as data streams. The method is based on the fact that nobody can hand write two identical patterns. The result of the authentication test is false if the new hand writing pattern is identical or too close to any of the previously stored patterns.