A portable ultrasonic imaging probe that is adapted to connect to a host computer via a passive interface cable. The probe includes an array of ultrasound transducers, a high voltage pulser for energizing transducers to emit an ultrasound pulse, analog signal processing circuitry that combines echoes detected by transducers into a single analog echo signal, am analog-to-digital converter that converts the analog echo signal into a digital echo signal; and interface circuitry that transfers the digital echo signal across the passive interface cable to the host computer.