An adapter for coupling to a process control transmitter of the type used to monitor a process variable in an industrial process, the adapter comprising: a first adapter connection (Loop+) coupled to a first wire of a two wire process control loop; a second adapter connection (Loop-) coupled to a first transmitter connection of the process control transmitter; a third adapter connection (HART@) coupled to a second transmitter connection of the process control transmitter and a second wire of the two wire process control loop, wherein the third adapter connection is configured to provide digital communication on the two wire process control loop; wireless communication circuitry configured to provide wireless communication for the process control transmitter, wherein the first and second adapter connections (Loop+, Loop-) are configured to power the wireless communication circuitry; a capacitor configured to store energy for use in operating the wireless communication circuitry; a regulator configured to perform a DC-DC conversion; a shunt circuit connected in parallel to the regulator and including a bypass transistor controlled by an operational amplifier, wherein a current through the bypass transistor is used to charge the capacitor, and wherein the regulator operates in series with the control loop and is in a feedback loop formed by the operational amplifier, and intrinsic safety circuitry coupled to at least one of the first, second and third adapter connections (Loop+, Loop-, HART ®) configured to limit energy transfer to a value which is less than a predetermined value, wherein the intrinsic safety circuitry is configured to limit the energy transfer which the wireless adapter discharges back into the two wire loop, and the two wire loop is further configured to carry information communicated from the third adapter connection, wherein the intrinsic safety circuitry is coupled in series between the capacitor and the at least one of the first, second and third adapter connections (Loop+, Loop-, HART ®). a first adapter connection (Loop+) coupled to a first wire of a two wire process control loop; a second adapter connection (Loop-) coupled to a first transmitter connection of the process control transmitter; a third adapter connection (HART@) coupled to a second transmitter connection of the process control transmitter and a second wire of the two wire process control loop, wherein the third adapter connection is configured to provide digital communication on the two wire process control loop; wireless communication circuitry configured to provide wireless communication for the process control transmitter, wherein the first and second adapter connections (Loop+, Loop-) are configured to power the wireless communication circuitry; a capacitor configured to store energy for use in operating the wireless communication circuitry; a regulator configured to perform a DC-DC conversion; a shunt circuit connected in parallel to the regulator and including a bypass transistor controlled by an operational amplifier, wherein a current through the bypass transistor is used to charge the capacitor, and wherein the regulator operates in series with the control loop and is in a feedback loop formed by the operational amplifier, and intrinsic safety circuitry coupled to at least one of the first, second and third adapter connections (Loop+, Loop-, HART ®) configured to limit energy transfer to a value which is less than a predetermined value, wherein the intrinsic safety circuitry is configured to limit the energy transfer which the wireless adapter discharges back into the two wire loop, and the two wire loop is further configured to carry information communicated from the third adapter connection, wherein the intrinsic safety circuitry is coupled in series between the capacitor and the at least one of the first, second and third adapter connections (Loop+, Loop-, HART ®).