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Bus monitoring analog camera selection and installation guide

(V1.0)

Attention: The cameras described in this guide refer to the analog camera with built-in pickup.

First, the camera selection

1) clarity

For color surveillance cameras, 420 TVL (TV line) are medium resolution surveillance cameras, and 480 TVL and above are high resolution surveillance cameras. The higher the clarity, the higher the price. For better image quality, we recommend using a camera of 480 TVL and above.

2) Focal length

The focal length is the distance between the lens and the photosensitive element. By changing the focal length of the lens, you can change the magnification of the lens and change the size of the captured image. Because car cameras usually use fixed-focus cameras, customers need to choose the right focal length camera according to their needs. The larger the focal length of the lens, the larger the magnification, the closer the zoom can be, the smaller the range of the picture, the more detailed the details of the distant view; the smaller the focal length of the lens, the smaller the magnification, the wider the range of the picture, the more visible Big scene. Commonly used lenses are 3.6mm, 6mm, 8mm, etc. The 3.6mm lens shooting angle is about 90°, the 6mm lens shooting angle is about 60°, and the 8mm lens shooting angle is about 45°.

3) Signal to noise ratio

It is required to select a camera with a signal-to-noise ratio greater than 48 dB. When the ambient illumination is insufficient, the image of the surveillance camera with higher signal-to-noise ratio becomes clearer.

4) Night Vision

In order to obtain visual effects at night, it is necessary to turn on the infrared fill light at night. The selected lenses are all infrared light, and the color of the pictures taken during the day is naturally disturbed by the infrared light. If you don’t want infrared light, use a color lens that is not transparent to infrared light, the picture will be vivid and clear, but you can’t take pictures in the dark.

In principle, the car camera uses a 15-meter infrared integrated dome camera with a 15 meter night vision distance, which automatically turns on the infrared light when low illumination.

5) Power supply

The power supply is 12VDC, and the maximum current of a single camera (infrared light) requires less than 400mA.

6) Interface

In order to ensure a high-reliability connection in a harsh environment, the interface of the AV and power supply is in principle selected from the female plug of the aviation plug.

Second, the use of recommendations

1. If you want to get a wide range of shooting, but the requirements for detailed images are not high, it is recommended to use a 3.6mm lens camera, such as shooting inside the car;

2. If the shooting range is not high and the detailed image is required, if you need to take the front license plate, it is recommended to use a 6mm or 8mm lens camera;

Example: The picture below shows a picture taken simultaneously with a 6mm lens and an 8mm lens. Under the same conditions, the picture of the car before the 8mm lens is more clear, but the picture taken by the 6mm lens has a larger angle and more content, and can completely capture the right front vehicle, while the 8mm lens can only capture parts.

6mm lens monitoring effect

8mm lens monitoring effect

3. When there is insufficient external light at night, the camera will turn on the infrared light (night vision), because the vehicle’s headlights will also turn on. At this time, when the front license plate is photographed, the shooting effect will be poor due to the windshield reflection, as follows The figure shows. Therefore, it is recommended to turn off the infrared light (night vision) function of the camera when using it in this case, and rely on the vehicle’s own light source or external light source such as street light to shoot. That is to say, when taking pictures through the glass, you cannot turn on the infrared light of the camera (night vision).

Because the reflective front license plate was photographed as white

4. If you make your own patch cord or extension cord to dock with the camera and pickup, you need to pay attention to the following:

1) Connect the video cable of the camera to a video coaxial cable with a characteristic impedance of 75 ohms to prevent interference from external signals;

2) To connect the audio adapter cable of the pickup, it is necessary to use a single-core shielded cable to prevent interference from external signals;

3) The power cable of the single-channel camera needs to use at least 22-gauge wire. The power cable length is ≤15m. Multiple camera power supplies cannot be connected to one set of power cables.

4) All wires must be flame retardant.

5. The camera of the tachograph is a camera-acoustic integrated structure, and the aviation plug interface contains the connection of video, audio and power. If you want to choose and install the pickup separately, you need to use an active pickup, power supply 12V.