Four experimental scalp electrodes for foetal monitoring, 1968.

These electrodes were designed to enable monitoring of the foetal heartbeat during childbirth. They are of the clip type and follow the design of Dr Edward Hon who was the collaborator of Dr Orvan Hes at Yale-New Haven Hospital during the development of the first foetal heart monitors in 1957. Before Hes' invention, obstetricians were unable to find a fetus' heartbeat because it was drowned out by the mother's beat and foetal distres was therefore not treated.