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:
Aug. 22, 1978
Filed:
Nov. 15, 1976
Andreas Scheidweiler, Uerikon, CH;
Cerberus AG., Mannedorf, CH;
Abstract
An ionization chamber is exposed to the atmosphere to be supervised, the ionization chamber being so constructed that the electrical resistance thereof changes in the presence of fire particles or aerosols upon occurrence of a fire; to improve reliability of detection, the ionization chamber is connected as a resistance element in a free-running multivibrator oscillator circuit, which includes a pair of cross-coupled field effect transistors (FET's) so that, upon change of the atmosphere to which the ionization chamber is exposed, the pulse frequency of the oscillator changes, which change is detected by a pulse rate detector. If the detector has upper and lower threshold levels, deviation of pulse rate in one direction may be used to sense presence of a fire, and in the other direction may be used to sense incipient trouble in the circuit itself.