American District Telegraph Company

Electro Signal Lab, Inc.

Robert B Enemark

Stephen Marchetti

Aaron A Galvin

Glenn F Cooper

Paul S Richtarcsik

An optical smoke detector having a conical masking body located directly between a light source and a light receiver. The masking body is provided with a reflecting surface so that rays from the light source are diverted into a reaction zone to supplement direct rays from the light source to the zone. In one embodiment the reflecting surface is cuspidate while in another embodiment a second masking body is added which shadows the light receiver from viewing the base of the first masking body.

Forward scatter smoke detector

For use in an alarm system, a security switch is provided, the transition state of which is detected by an associated circuit and a coded signal transmitted along a communication path indicative of the transition state, this coded signal being received and decoded to provide an output indication of the switch state.

Coded security switch

An electronic sounder employs a pair of piezoelectric oscillators tuned to different frequencies to provide loud raucous sound. The sounder is especially suited for providing audible indications of an alarm condition which is sensed by an associated alarm system.

Electronic sounder

A detector of a significant gas condition in the atmosphere comprises one or more elements for sensing the condition, the elements being connected to an alarm channel which sounds a warning alarm or controls a corrective device such as a gas valve in the event of an excessive atmospheric condition. The detector includes a threshold sensing and alarm amplifying channel, and a trouble sensing electronic valve or stage responsive to failure of one of the sensing elements both to enable operation of a trouble channel to cause the alarm to indicate the failure and also to inhibit operation of the alarm channel. The trouble channel may also relay power supply failures such as a decrease in battery voltage.

Dual alarm gas detector

An optical smoke detector with a clock pulsed light source and photodiodes responding to smoke scattered light includes an alarm initiating logic circuit which delays the initiating of alarm while several samplings of smoke are sensed and then latches the logic circuit in alarm condition.

Latching alarm smoke detector

A scatter type of smoke detector wholly supplied by a dry cell battery includes a clock circuit applying energy pulses to an LED light source which directs light pulses on a smoke sensing path. Light pulses scattered by smoke generate detection pulses in a photo diode whose amplitude is dependent on the smoke density. The clock pulses and detection pulses are applied to a control circuit including a dual, data-type flip-flop logic circuit and a threshold circuit driving an alarm horn. If the smoke density, and hence the detection pulse amplitude, exceeds a predetermined level the control circuit energizes the alarm in a continuous mode. If the battery drops below a preselected level the control circuit is actuated in an intermittent mode.

Battery powered smoke detector

A scatter type of battery smoke detector includes a clock circuit applying energy pulses to an LED light source which directs light pulses on a smoke sensing path. Smoke entering the light path scatters pulsed light to a photodiode whose output voltage varies with smoke density and corresponding light pulse level. A threshold stage responds to photodiode voltage above a threshold level to generate a detection pulse. The detection pulses and clock pulses are applied to a control circuit including a dual data-type flip-flop logic circuit, and thence to a threshold circuit driving an alarm horn. If the smoke density and hence the detection pulse amplitude exceed a predetermined level, coincident application of the clock and detection pulses to the control circuit will cause the control circuit to respond by energizing the alarm continuously so long as the detection pulses recur at the clock frequency. If a spurious noise voltage should coincide with a clock pulse the control circuit will energize the alarm, but only for the brief inter-pulse interval. To reduce battery drain the inter-pulse is made relatively long by design of the normal clock circuit time constant. But, to reduce the time that a spurious alarm can sound, the clock circuit time constant is shortened substantially when the control circuit responds to coincident pulses.

Variable frequency light pulser for smoke detectors

A battery powered smoke detector includes a battery powered discriminator circuit which periodically senses the chemistry of the battery represented by its volt-ampere output and internal impedance. An external impedance comparable to the alarm circuit load on the battery is connected in parallel with the battery such as to trigger an alarm when the battery energy delivered through the impedance approaches a level inadequate to drive the alarm.

Battery discriminator circuit for smoke detectors

A simplified smoke or other particle detector circuit includes a light emitting diode in series with a compensating photocell and a photocell sensing LED light scattered from particles. In parallel with the LED is a high resistance, and in parallel with the photocells is a low resistance, the resistances having a common junction coupled to a threshold circuit input as is the output of the photocells. Sensing smoke produces a photocell output which triggers the threshold device to generate an alarm signal. Failure of the LED produces a voltage at the resistance junction which similarly triggers the threshold device to alarm.

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Duxbury, MA, United States of America

Robert B Enemark