Abstract: A smoke detector includes: a casing; a first light emitting unit; a second light emitting unit; and a light receiving unit. A second scattering angle that is an angle between the reception axis of the light receiving unit and a second extension extending from an intersection of the second emission axis and the reception axis in a direction away from the second light emitting unit is larger than a first scattering angle that is an angle between the reception axis of the light receiving unit and a first extension extending from an intersection of the first emission axis and the reception axis in a direction away from the first light emitting unit.

Abstract: A digital controller includes a microprocessor for receiving a signal indicating a process variable from a process and calculating a manipulated variable in accordance with a predetermined algorithm in order to cause the manipulated variable signal to follow a desired setpoint variable. An operation data output system delivers an output signal to the process which holds the operation output value from the microprocessor. The controller also has on an electronic indicator for displaying the process variable, the setpoint variable, and the manipulated variable, and a driver for receiving the process variable signal and the setpoint variable to drive the electronic indicator. The driver further receives the manipulated variable from the operation data output system for driving the electronic indicator, whereby the controller is capable of displaying the manipulated variable on the electronic indicator should the microprocessor fail.