The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 02, 1986
Filed:
Jul. 16, 1984
Manley S Keeler, Naperville, IL (US);
Pittway Corporation, Aurora, IL (US);
Abstract
A photoelectric combustion products detector for periodically sampling the ambient air includes a sampling circuit capacitively coupled to an AC source, so that the coupling capacitor produces at the sampling circuit a source current 90.degree. out of phase with the AC source voltage, which is rectified to provide a supply voltage. Sampling is controlled by a NAND gate having at its inputs a varying threshold level which is proportional to and in phase with the supply voltage. A ramp signal generator connected to one gate input terminal enables the gate when the ramp signal exceeds the varying threshold level. The other input terminal of the gate is connected to a timing circuit comprising a Zener diode, a capacitor and a discharge resistor which produces a short trigger pulse at or near each positive zero crossing of the AC source voltage, the coincidence of a trigger pulse with an enabling period causing the gate to actuate the sampling circuit.