Left panel: the force-frequency relation builder device. Right panel: force-frequency recording during bycicle semi-supine stress echo. The transcutaneous force sensor was housed in a small case which is positioned in the mid-sternal precordial region and is fastened by a solid gel ECG electrode. The acceleration signal is converted to digital and recorded by a laptop PC, together with an ECG signal. The system is also provided with a user interface that shows both the acceleration and the ECG signals while the acquisition is in progress. The system is portable, and the remote transmission is feasible and simple.