A security system for a building comprises a pressure sensor and a computer system communicatively coupled with the pressure system. The pressure sensor coupled to a movable portion of a window in the building. The computer system is configured to: receive a first pressure measurement from the pressure sensor; compare the first pressure measurement to a reference pressure measurement; and based on the comparison, detect that the movable portion of the window has moved.

A method of rotating a surveillance camera having an acceleration sensor and being controllable by a processor to maintain a tilt-angle to conform to a command tilt-angle, includes the steps of moving the surveillance camera tilt to a predetermined command tilt-angle in response to a signal from the processor; periodically calculating estimated tilt-angles by using acceleration values in at least one axis of an acceleration sensor; calculating a difference value between an estimated tilt-angle of a current period and an estimated tilt-angle of a previous period; and when the difference value between the estimated tilt-angles exceeds a set limit, moving the camera to another position to correct the tilt angle according to the difference calculate.

In a general aspect, an offline system detects new motion zones for a motion detection system. In some examples, observed channel response data is obtained from a motion detection system. The observed channel response data is associated with a plurality of subcarriers for each wireless link over a period of time. Estimated channel response data is generated for each wireless link. Transitions between zones of activity are identified in the estimated channel response data for each of the plurality of subcarriers for each wireless link. A new motion zone of the motion detection system is detected based on the estimated channel response data and the identified transitions.

In a general aspect, an offline system detects new motion zones for a motion detection system. In some examples, observed channel response data is obtained from a motion detection system. The observed channel response data is associated with a plurality of subcarriers for each wireless link over a period of time. Estimated channel response data is generated for each wireless link. Transitions between zones of activity are identified in the estimated channel response data for each of the plurality of subcarriers for each wireless link. A new motion zone of the motion detection system is detected based on the estimated channel response data and the identified transitions.

Environmental monitoring devices for detecting and warning users of unhealthy levels of a given substance are disclosed having more than one sensor for each substance to be detected. A processing unit, wirelessly coupled to the sensors in the devices can be configured to receive each of the output signals from the sensors, determine a detection signal for the substance based on the output signals, determine a gain of a majority of the sensors, and generate a calibration action responsive to the output signals deviating by a threshold amount, wherein the calibration action comprises adjusting a gain of a deviating sensor to correspond with the gain of the majority of sensors.

Environmental monitoring devices for detecting and warning users of unhealthy levels of a given substance are disclosed having more than one sensor for each substance to be detected. A processing unit, wirelessly coupled to the sensors in the devices can be configured to receive each of the output signals from the sensors, determine a detection signal for the substance based on the output signals, determine a gain of a majority of the sensors, and generate a calibration action responsive to the output signals deviating by a threshold amount, wherein the calibration action comprises adjusting a gain of a deviating sensor to correspond with the gain of the majority of sensors.

Examples of systems and methods for locating movable objects such as carts (e.g., shopping carts) are disclosed. Such systems and methods can use dead reckoning techniques to estimate the current position of the movable object. Various techniques for improving accuracy of position estimates are disclosed, including compensation for various error sources involving the use of magnetometer and accelerometer, and using vibration analysis to derive wheel rotation rates. Also disclosed are various techniques to utilize characteristics of the operating environment in conjunction with or in lieu of dead reckoning techniques, including characteristic of environment such as ground texture, availability of signals from radio frequency (RF) transmitters including precision fix sources. Such systems and methods can be applied in both indoor and outdoor settings and in retail or warehouse settings.

Disclosed is an alarm device for detecting a hazard in a control zone, the alarm device having: a hazard sensor that comprises a configurable sensitivity level and a device controller that controls the sensitivity level of the hazard sensor, wherein the alarm device: receives over an electronic network a target sensitivity, and calibrates the hazard sensor to achieve the target sensitivity level.

A driver circuit and a method of supplying a constant current to the light emitter of the smoke detector are disclosed. The driver circuit includes a transistor, and a controller. The collector terminal of the transistor is connected to the light emitter and a resistor is connected to the emitter terminal. During the manufacturing stage, the controller monitors and stores the values of first base voltage to be supplied to the base terminal to supply a constant current to the light emitter, and first resistor voltage across the resistor when the first base voltage is supplied to the base terminal. Before each smoke detection process, the controller processes the stored data and adjusts the base voltage to be supplied to the base terminal to enable the transistor to supply the constant current to the light emitter, regardless of the temperature around the smoke detector.

A driver circuit and a method of supplying a constant current to the light emitter of the smoke detector are disclosed. The driver circuit includes a transistor, and a controller. The collector terminal of the transistor is connected to the light emitter and a resistor is connected to the emitter terminal. During the manufacturing stage, the controller monitors and stores the values of first base voltage to be supplied to the base terminal to supply a constant current to the light emitter, and first resistor voltage across the resistor when the first base voltage is supplied to the base terminal. Before each smoke detection process, the controller processes the stored data and adjusts the base voltage to be supplied to the base terminal to enable the transistor to supply the constant current to the light emitter, regardless of the temperature around the smoke detector.