Both beams are then collected onto the photodetector where optical heterodyne detection is used to extract the Doppler signal.

The arterial blood flow was confirmed by an audible Doppler signal and the curve recorded (Fig 2).

They started this work in July 1958 and in the same year detected ultrasonic Doppler signals from arteries and veins at the skin surface.

Using an ultrasonic scanner, the flap-pedicle is centre-aligned upon the Doppler signal of the supraorbital artery.

This smears out, or blurs, the Doppler signal.

Capillary refilling time, Doppler signals, pulse oximetry, and sensation distal to the burned area should be checked every hour.

Subsequently, any increase in capillary refill time, decrease in Doppler signal, or change in sensation should lead to rechecking the compartment pressures.

"And here comes our Doppler signal."

On January 3, 1934, a Doppler signal was received by reflections from the aircraft at some 600 m range and 100-150 m altitude.

Spikes may be caused by aliasing of the Doppler signal.