Abstract: An environmental monitoring system in which a controller is arranged to test the workability and reliability of a plurality of detector units on a cyclic basis. Each unit has an analog sensor and an analog to digital converter for converting the analog sensor voltage to a digital value in a range of 0 to N. Each unit responds to a test instruction to cause the sensor analog output to assume an alarm value. The sensor output is limited to a maximum value that under a no drift condition of the analog to digital converter, its corresponding digital signal value will be intermediate a tolerance range of values, the upper limit of such range being less than N. The controller includes a test routine program for both issuing the test instruction and for determining if the digital signal test value is within the tolerance range and issuing a trouble output indicative of the test value being outside the range.

Abstract: A photoelectric smoke detector which operates on the scattered light principle and involves a light source, and a photosensor placed at an angle to the light beam such that it is normally not illuminated, the light source and photosensor being located within a dark detection chamber having air entry ports that restrict ambient light; smoke particles entering the smoke chamber produce interruption of the light beam, thereby scattering light onto the photosensor. The detection chamber is formed within a cup-shaped grill which can be readily removed from the housing by rotation of the grill to disengage a locking mechanism; the grill is provided with an end wall and, integrally formed therewith, spaced inner and outer cylindrical side walls, the inner side wall being defined by baffles which include scoop fins that are used to trap light, but which also function to scoop air into the chamber and cause air turbulence for mixing the smoke particles thoroughly; the outer side wall having windows for entry of smoke.

Abstract: A photoelectric smoke detector operating on a scattered light principle. The photosensor is connected at the input of an operational amplifier, such amplifier functioning as a threshold detector, saturation pulse amplifier and fixed pulse width compensator. Another feature of the invention resides in the provision of a special RC network connected from the output of a first transistor of a flasher section or subcircuit, which provides pulse power to the light source, to the input of a second transistor in such flasher circuit. As a consequence of this arrangement, when the LED serving as the light source tends to age, with a corresponding increase in its impedance, an appropriate signal is fed back from the aforenoted output of the first transistor to the input of the second, thereby to increase the pulse width of the output signal through the LED such that it is no longer, thereby compensating for the fact that it is no longer as bright.

Abstract: An ionization smoke detector having a sensing chamber and including: a screen or mesh electrode enclosing and forming the outer limits of said sensing chamber, while fully exposing said sensing chamber to the ambient atmosphere; a baffle means covering said electrode and in close proximity thereto, said baffle means having a plurality of slit-like openings spaced around the periphery thereof for permitting the transfer of ambient atmosphere to said sensing chamber; said openings of said baffle means constituting deflectors oriented to deflect any air currents directed normal to the surface of said baffle means so the air currents will enter said sensing chamber at an angle other than said normal angle.

Abstract: An ionization smoke detector device including means for insuring that adjustment can be made in the triggering potential for the alarm device so that should circumstances change, an operator can make a simple adjustment to take into account the changed circumstances. This means comprises a programmable Zener diode which is connected to a voltage dividing resistance network at the output of a field effect transistor, the other end of the Zener diode being connected to the input of a silicon controlled rectifier device which functions to trigger the alarm.Another primary feature of the present invention is the provision of a means for testing the operation of the system in such a way that all of the elements of the system will be tested rather than merely some of them.