An implantable medical device capable of being placed between a first operational mode and a second operational mode. The medical device comprises a magnetic field sensing device for outputting a signal in response to sensing a magnetic field. The medical device further comprises a logic circuit for continuously asserting the signal during a time period when the neurostimulation device is in the first operational mode, and intermittently asserting the signal during at least one time period when the neurostimulation device is in the second operational mode. The medical device further comprises a delay circuit for introducing a time delay into the asserted signal, the time delay being less than the time period, but greater than each of the at least one time period. The medical device further comprises control circuitry for performing a function in response to receiving the delayed signal at a first input terminal.