what is Multiplexer?

In the multi-camera surveillance system, it is usually found that multiple pictures show on one monitor together. When adopted, multiplexers can make monitors which are as the same as multiplexers in number, display signal of all channels on one monitor at the same time. By such way, it achieves not only decreasing quantity of camera, but also for user watching each surveillance area more conveniently. The most found multiplexers can be 4 pictures, 9 pictures and 16 pictures etc. In other words, there can be 4、9 or 16 channels video showing on one monitor together, even these videos can be transmitted to video recorder to be recorded.