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. 09, 1986
Filed:
Oct. 30, 1984
Alfred R Brown, Stanwell, GB;
Richard A Whetton, Maidenhead, GB;
Graviner Limited, Buckinghamshire, GB;
Abstract
A fire detecting arrangement has a longitudinal fire detector having conductors separated by a substance whose resistance decreases with temperature and whose charge acceptance capability increases with temperature. The detector is supplied with a rectangular waveform swinging between +5 and -5 volts through resistors, one of which is high compared with the other. High temperature will therefore cause a greater volt drop across the detector during positive waveform portions than during negative waveform portion, the potential division effect of the unequal resistors being enhanced by the increased charging current. Contamination or damage merely decreases the resistance of the detector and the lack of charging current means that the inequality of the voltage drops during positive and negative portions of the drive waveform is not so marked. A comparator compares the voltage across the detector with different reference levels at predetermined time instants synchronised with the drive waveform to produce digital signals which are fed to shift registers to cause a 'fire' or 'fault' warning to be produced.