US Patent 7915761 Power injector detection

In one embodiment, a signal detector is coupled to an external power source. The signal detector is configured to ascertain whether a predetermined signal was received from the external power source. Control logic is coupled to the signal detector and to the external power source. The control logic is responsive to the signal detector to determine a characteristic of the external power source based on whether the signal detector detected the predetermined signal. The characteristics of the external power supply can be determined based on the frequency, amplitude and duration of a signal received from the power injector. This enables the control logic to determine the power available from an unknown power supply and to configure a device to operate accordingly.