THE DVR-USB42A IS A DVR (PC) BOARD TYPE → 4 CH. USB DVR

Yes, DVR senses pixel movement of the video signal from the camera. So a DVR (built-in or separate) will detect motion when the camera is placed behind a window or glass barrier

Other info:
Since you can have the DVR record only upon motion, you can extend the recording time period which it is intended to cover. Each 1GB of memory will record up to 2.5 total hours of video.. However Since the camera and the DVR has to be on all the time, it will not extend the battery life. Typically, 1GB of memory will record up to 2.5 total hours of video (depending on the model).
Also, you can configure to eliminate certain areas of the picture from motion detection. Example would be deactivating lower 1/5 of the screen that would not capture creatures that enter only that part of the image.
Motion detection sensitivity is adjustable as well.

Full size stand alone DVRs all come with a cooling fan that will make noise as much as a PC. Portable DVRs do not make any noise.

Yes, there is a loop mode for recording. When the memory is full, it will start to record from the beginning of the memory. In other words, you will always retain certain amount of most recent data.

DVR senses pixel movement of the video signal from the camera. Since you can have the DVR record only upon motion, you can extend the recording time period which it is intended to cover. Each 1GB of memory will record up to 2.5 total hours of video.. However Since the camera and the DVR has to be on all the time, it will not extend the battery life. Typically, 1GB of memory will record up to 2.5 total hours of video.
Also, you can configure to eliminate certain areas of the picture from motion detection. Example would be deactivating lower 1/5 of the screen that would not capture creatures that enter only that part of the image.
Motion detection sensitivity is adjustable as well.

DVRs provide video recording on to its hard disk or a removable flash memory. Other features includes: multi video inputs, motion detection recoding, networking etc...

Does your cameras work with different voltage for other countries?

Most of our camera come with a power adapter that can handle form 110V ~240V AC.
In case of a direct AC plug-in camera such as clock radio camera
We will include the 220V to 110V (60Hz) step-down converter.
However, if your country uses 50Hz, the time on the clock, because it is digital, will not be correct (off about 20 min a day)