Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
A: original devices with LEDs and photodiode for signal excitation and reception (bottom side) and electronics (upper side). B: the devices are shielded by copper foil, only the LEDs, the photodiode and the battery plug are spared. The device is powered by a small battery that was covered in copper foil, too.
