Smoke detector
First Claim
1. In a smoke detector of the type wherein an alarm signal is generated to activate an audible indicator, and wherein an oscillator circuit drives a pulsating visual indication of stand-by readiness with the frequency of the oscillator being derived from the charge rate of a capacitor, the improvement comprising:
- a current source connected to the capacitor;
mode control switch means for interrupting flow from said current source to the capacitor, said switch means having a control electrode to which the alarm signal is applied, the frequency of the oscillator being increased during the alarm signal when said current flows through said switch means to increase the charge rate of the capacitor; and
duty cycle means for controlling the operative period of the audible indicator during each cycle of increased oscillator frequency.
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Accused Products
Abstract
In a smoke detector of the type wherein an alarm signal is generated to activate an audible indicator and an oscillator circuit drives a pulsating visual indication of standby readiness, the oscillation frequency increases between its standby and alarm modes. In addition, duty cycle means controls the operative period of the alarm indicator during each cycle of the increased frequency. The smoke detector includes a relaxation oscillator where the oscillation frequency is proportional to the charge rate of a capacitor. Independent current sources are connected through separate switches to change the charge rate of the capacitor and thus the oscillation frequency. Each switch is controlled by signals from a separate detector of a condition which requires that the oscillation frequency be changed, for example, the presence of smoke.
18 Citations
5 Claims
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1. In a smoke detector of the type wherein an alarm signal is generated to activate an audible indicator, and wherein an oscillator circuit drives a pulsating visual indication of stand-by readiness with the frequency of the oscillator being derived from the charge rate of a capacitor, the improvement comprising:
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a current source connected to the capacitor; mode control switch means for interrupting flow from said current source to the capacitor, said switch means having a control electrode to which the alarm signal is applied, the frequency of the oscillator being increased during the alarm signal when said current flows through said switch means to increase the charge rate of the capacitor; and duty cycle means for controlling the operative period of the audible indicator during each cycle of increased oscillator frequency. - View Dependent Claims (2, 3, 4, 5)
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Specification