An access port for providing subcutaneous access to a patient, and a method of identifying a subcutaneously implanted access port. Unlike conventional fluid transfer systems, the present apparatus allows for the pressure in the transfer tube to be balanced to internalize the pressure forces and prevent the exertion of pressure forces on the sub-systems connected to the transfer tube. The torque to current converter transforms a torque signal into a current signal. Moreover, the slide rail and the guide rail that match each other between the slideway and the bottom of the nipper prevent the nipper from deviating when sliding along the slideway for more labor-saving use.