Installing the camera everywhere is becoming feasible now, thanks to the decreasing price of security cameras. However, providing a dedicated monitor for every installed camera is not efficient. In addition, the CRT monitor might suffer phospor burn if it used to display static image from only one camera. Video switcher circuit is needed to display more than one display in one monitor. Take a look at below circuit schematic :
MAX454 is the core of this video. It is a video multiplexer-amplifier assembled by MAXIM Semiconductor. Pay attention when designing the video signal path around this chip. Track of ground plane can be inserted between video signal channels to prevent crosstalk and noise interference. The chip should directly soldered to the PCB. A CD4017 sequencer which drive the channel indicators (LED1-LED4) can be seen here. The output will decode 2 bit binary data by D1..D4 to address MAX454 multiplexer. The output of this sequencer also drives the indicators.