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:
Jul. 26, 1977
Filed:
Sep. 16, 1975
John Dobrzanski, New Britain, CT (US);
Emhart Industries, Inc., Farmington, CT (US);
Abstract
An ac powered smoke detector utilizes an ionization chamber as the sensing element and a threshold circuit including a programmable unijunction transistor for activating an annunciator device such as a horn. An ac-to-dc converter provides regulated dc power to the chamber, the threshold circuitry and the annunciator for operation. When a specified level of smoke exists within the chamber, the programmable unijunction transistor is placed in the conductive state and produces a non-latching activating signal which energizes the horn. To insure that the programmable unijunction transistor makes a positive transition into the conductive state at the threshold level, the anode-cathode circuit of the transistor and the transistor itself are jointly selected to provide an anode current greater than the characteristic valley current of the transistor when the threshold level is reached.