Abstract: An ionization smoke detector is provided with a ventilated sensing chamber and housing which cooperate to improve and control smoke sensitivity by reducing adverse effects of external winds or drafts. The detector includes a housing having arcuate openings arranged in a circle and a flared deflector mounted within the circle in order to direct smoke and other particulate matter into the interior of the housing. A smoke sensing chamber is positioned within the housing adjacent the openings and has a cylindrical shell electrode defining arcuate ventilating apertures registering with the arcuate openings of the housing to pass smoke and particulate matter in and out of the chamber in cooperation with the flared deflector. The shell electrode and the housing cooperate to control the flow of smoke through the chamber and thereby improve smoke sensitivity.

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.

Abstract: An ionization smoke detector particularly suited to residential use is battery-operated and is connected with a non-latching, pulsating alarm circuit. The detector has a sensing chamber formed by a perforated metallic shell and an electrode within which an insulated radiation source is centrally positioned to generate an ionization current for detecting smoke or other similar aerosols. The alarm circuit provides a pulsating alarm signal when smoke levels above a predetermined value are sensed. The alarm circuit also includes a low voltage detection circuit for sounding the alarm when the end of useful battery life is approaching.

Abstract: An ionization smoke detector particularly suited to residential use is disclosed. The detector is battery-operated and is connected with a non-latching, pulsating alarm circuit. The detector has a sensing chamber formed by a perforated metallic shell and an electrode within which an insulated radiation source is centrally positioned to generate an ionization current for detecting smoke or other similar aerosols. The alarm circuit provides a pulsating alarm signal when smoke levels above a predetermined value are sensed. The alarm circuit also includes a low voltage detection circuit for sounding the alarm when the end of useful battery life is approaching.