Abstract: An implant for stimulating the vagus nerve receives commands over a radio frequency link. The communication protocol uses asynchronous communications devices with parity checking and echoing of communicated characters and passwords to improve communication error checking. The implant disables a voltage convertor used in providing the stimulation signal at periodic intervals to monitor for communications attempts. The implant provides radio frequency marker pulses before providing stimulation signals of certain frequencies. During the providing of stimulation signals the implant monitors the voltage overhead present between the voltage source and the load and adjusts the overhead to a desired level. The implant changes the voltage applied to certain internal components during stimulation periods to allow full power operation during those intervals and reduced power levels at other intervals.