Q:20 meters away with the number of mm monitor camera lens appropriate?

According to the imaging principle, the smaller the focal length, the wider the field of view, but the distance is not clear. The larger the focal length, the narrower the field of view, but the longer the distance will be clearer.

Q:An accurate calculation formula for monitoring the focal length and actual distance of the lens

So when you need to monitor the panorama to see the local, the general should consider the use of electric two variable or electric three variable lens. Of course, in the selected lens under the premise of the use of high-resolution cameras and monitors can be monitored objects in the smaller size can also see the local details.

Q:Does the infrared surveillance camera automatically alarm when someone enters the monitoring range?

General camera is not the end of the low-end camera does not have this function, you can use the alarm to linkage, the alarm through the infrared detection of some people come in, will alarm. There is an automatic monitoring area of the camera can be, once someone appears in a certain area will be the alarm, similar to the road to shoot the kind of red light. Very sensitive, but the cost is relatively high. The best infrared camera can find 300 meters of people, but it is expensive.

Q:Police surveillance camera and civilian What is the difference?

Such as prisons, interrogation rooms, etc., need to use the explosion-proof damage to the camera, the police need to use the car head (plus lift rod), due to the increase in functionality, the cost will be relative to the increase, these are civilian do not need.

Q:Monitoring camera POE power supply is good, or centralized power supply good?

If you have to use (see profits, you understand), it is recommended to choose some big brands of products, such as Huawei, 3com, etc., the cost is high, 20 meters if the use of oxygen-free copper feet .5 super five twisted pair , The loss on the wire can be ignored, but the use of POE power supply to consider the lightning ah, a break is a big string ah! :) POE to be used to do lightning protection measures Oh. And POE power supply in the event of failure when the investigation than the use of some trouble with the transformer.

Q:There are cameras at the fork in the expressway

The first speed camera is a shape like a rectangular box, play a decisive role is actually connected with the radar module. Radar detection vehicle over speed will be linked when the camera to take pictures of evidence. The speed radar uses the Doppler effect principle. When the vehicle approaches the radar antenna, the reflected signal frequency will be higher than the transmitter frequency. When the vehicle is away from the antenna, the reflected signal frequency will be lower than the transmitter rate. This can be calculated by the frequency of the value of the target and the relative speed of the radar.

Q:Office area monitoring camera how to choose?

1, because the hemispherical can be ceiling on the ceiling, more beautiful

Q:The monitor camera does not display the image on the display

If the power is turned on, but the display no image display, is a blue background and "OFF" words, then the display menu to open the corresponding channel can display the image out.

Q:I would like to install at home and back door two cameras in general how much money?

According to the length of the cable, the camera's clarity is good or bad, a good camera generally a 160 or so can, the two together also 500 almost.

Q:Surveillance video can only save 4 days (the original can save about 15 days), is not the hard disk video recorder is a problem?

You are not modified to save the format of the ~ !! You can choose to format the hard disk ~ !! Clear all the contents of the inside to see