Abstract: A composite case of an airborne ultrasonic transducer for transmitting, receiving, or both of ultrasound in atmospheric environment at an ultrasound pressure level is disclosed. The case comprises a first case component and at least a second case component. The second case component is made of a material different from the first case component having an acoustic impedance smaller than that of said first case component and is structurally connected to the first case component for reducing said mechanical quality factor while maintaining said ultrasound pressure level. The connection between the first and second case components is by strong bonding at an interface between the components so that the strong bonding forms a composite structure for the case.

Abstract: A composite case of an airborne ultrasonic transducer for transmitting, receiving, or both of ultrasound in atmospheric environment at an ultrasound pressure level is disclosed. The case comprises a first case component and at least a second case component. The second case component is made of a material different from the first case component having an acoustic impedance smaller than that of said first case component and is structurally connected to the first case component for reducing said mechanical quality factor while maintaining said ultrasound pressure level. The connection between the first and second case components is by strong bonding at an interface between the components so that the strong bonding forms a composite structure for the case.

Abstract: The present disclosure illustrates a code activation device used to transmit an activation signal to a back-end device, so as to activate the back-end device. The code activation device comprises a sensing module and a processing module. The sensing module comprises a sensor unit, and the sensor unit generates sensing signals according to a preset action of a trigger object. The processing module connected to the sensing module receives the sensing signals, generates a sensing beat according to interval periods between the sensing signals, and determines whether the sensing beat matches a preset beat, wherein the processing module generates the activation signal when the sensing beat matches the preset beat.

Abstract: A composite case of an ultrasonic transducer for transmitting, receiving, or both of ultrasound is disclosed. The case comprises a first case component and at least a second case component. The second case component is made of a material different from the first case component and is structurally connected to the first case component by strong bonding at an interface between the components so that the strong bonding forms a composite structure for the case.