A sensor device, a holster sensing system, and a video-recording system are provided. The sensor device includes a control unit and a sensing module. The sensing module includes a reference coil set and an induction coil set that are arranged in a stacked structure. The sensing device is fixed on a holster. The induction coil set is configured to be adjacent to the holster. The control unit determines whether a gun is in the holster according to an inductance change between a sensing value generated by the induction coil set and a reference level provided by the reference coil set. In an application of the video-recording system, the control unit transmits a trigger signal to a recording device if the gun is determined to be pulled out of the holster according to the inductance change, so that the recording device is activated to start recording.

A system is provided for calculating and displaying an estimated remaining runtime for a portable generator. The system may include fuel sender with capacitive sensors communicating with a control system to display the fuel level and/or remaining runtime that can be recalculated when step changes in system performance are detected.

This invention discloses a door-window sensor which can be integrated with the associated fittings of the door and window. The sensor cannot be seen from appearance of the door and window, thus making the door and window beautiful and elegant on the whole. It can be installed easily without the limitation of door and window in the external dimension; it is used to determine whether the door and window is locked or closed; its cost is at a lower level. For the sensor, the door and window consists of frame and leaf. The leaf is driven by the motor to rotate around the connected axis and locked to the frame by means of lock. It gets close to inner side of the frame when closed and away from inner side of the frame when opened. The sensor consists of induction generating components, inductive device and data processing unit. One of the induction generating component and inductive device is arranged on the outside of leaf corresponding to the lock and the other is arranged inside the frame corresponding to the lock hole. The data processing unit is arranged outside or inside the door and window. State change of the inductive device is sent to the data processing unit by wired and/or wireless means.

The invention relates to a system of consumption meters (2) arranged in a communication network, where program data of the consumption meters can be updated via the communication network. A data collector (3) is arranged for updating the program data of a group of consumption meters over the network. This is performed by establishing a dedicated update session to each consumption meter of the group of consumption meters, and transmitting addressed update program segments to consumption meters in session. During the update session with a given consumption meter, any other consumption meter which is within communication range (8) will, if it receives the update segment, store it even though the segment is addressed to another meter. In an update session of a next meter, only segments not already stored from a previous session to another consumption meter are transmitted to the next meter.