Figure 3.

A prototype of the wireless trans-dermal photoelectric pulse wave monitoring system (DENSO, Japan). Panels A, B and C show a pulse wave sensor unit that applies green light to the skin and detects the reflected light through a small window (panel B) on the reverse side of the unit facing to the skin. The sensor unit transmits pulse wave signal to a receiver unit (panel D). The receiver unit has a small personal computer with LCD. The unit also has a slot used for charging the battery of the sensor unit.