The STB Self-checking Optical Touch Button is a photoelectric-based, manual activation device designed to provide an ergonomic alternative to conventional mechanical push buttons and palm buttons. The STB creates a pulsed infrared beam that spans its touch zone. The buttons switch when their light beam is broken by a simple insertion of a finger. No pushing is necessary, eliminating the hand, wrist and arm stresses that may result from repeated push button operation. This reduces harmful tendon, nerve and neurovascular disorders. The STB features a new internal design based on dual microcontrollers. When the STB is activated, two separate outputs (one normally-open and one normally-closed) change state. The patent-pending STB circuit uses a diverse-redundant, self-checking design, that will detect an internal safety-critical circuit fault and immediately switch its outputs to the OFF state. It's designed to be used with Category 4, Type IIIC Two-Hand Control devices per EN 574. These devices monitor the STB outputs, detect the output change of state and respond accordingly.