Transducer

A transducer can both send the pulse and detect its return.

An ultrasound scanner uses a transducer to send pulses into the body and detect their returning echoes. Some ultrasound is reflected where one type of tissue meets another, for example at a boundary between fluid and soft tissue. The scanner uses the time taken for each echo to return, together with the speed of sound in the tissue, to work out the depth of that boundary.