Abstract: An automatic system for calibrating gas sensors comprising a source of SPAN gas and a source of ZERO gas, and a means to control the flow of these gases to sensors. The system schedules and makes all required sensor value corrections and adjustments without human intervention. High resolution monitoring enables life extensions for the sensors, as well as higher accuracy monitoring than would be reasonably expected from low cost sensors.

Abstract: A field monitoring and communication system for arranging circuits and components for environmental and other types of monitoring systems includes: (a) microprocessor-based modules for communications and a variety of input/output types and combinations: (b) remote and optionally, proximal calibration and regulator modules: (c) a variety of sensor inputs optionally comprising intrinsically safe barriers.

Abstract: An automatic system for calibrating gas sensors comprising a source of span gas and a source of zero gas, a means to control the flow of these gases to sensors. The system makes all required sensor value corrections and adjustments without human intervention.

Abstract: An obscuration type optical smoke monitor is provided for use particularly in dusty and dirty environments. The smoke monitor comprises a housing enclosing a smoke monitoring chamber; two access ports located opposite each other on the housing; a shunt air flow path located between said two access ports; means to conduct air from said access ports through an optical chamber; a light emitting diode at the first end of said optical chamber, which light emitting diode produces a light beam axially through the center of said optical chamber; a photo transistor at the second end of said optical chamber to receive the light bean and issue an electrical signal proportional to the received light intensity; and an electronic module which provides variable electronic output, generating an analog output essentially proportional of the optical obscuration caused by the smoke.