A positioning system includes a console, an ultrasound probe, a stylet, a stylet control module, and an external sensor. The console includes a display. The ultrasound probe is designed to communicate imaging information to the console. The stylet includes a radiating element capable of producing an electromagnetic field, the electromagnetic field providing electromagnetic field information. The stylet control module includes a timer circuit designed to send electrical pulses at a pulse signal frequency to the radiating element. The external sensor is designed to detect the electromagnetic field and to determine a position of the radiating element with respect to the external sensor as the stylet is advanced in a vasculature of a patient, the external sensor designed to communicate the electromagnetic field information to the console. The system may include a circuit configured to synchronize at least one of the console and the external sensor with the pulse signal frequency.
