Application of 485 hubs in security monitoring systems

In existing monitoring systems, the matrix host, control keyboard host, and hard disk recorder are usually separate components. However, in some special cases, they need to coexist in one monitoring system. In this case, a 485 sharing device is needed to share multiple 485 input ports into a single 485 output port, and control the PTZ camera through a unified 485 output port.

In a video surveillance project for a residential community, the property management department required two monitoring centers, master and slave, to view and control the pan-tilt-zoom (PTZ) cameras throughout the community. Furthermore, each monitoring center was required to control the PTZ cameras via a matrix host to monitor the entire community, and to record video of the community's activities via hard disk recorders. Therefore, it was essential that multiple master control devices coexist within a single monitoring system.

During construction, the contractor discovered that simply connecting the matrix switcher and DVR in parallel to a single 485 bus caused the entire monitoring system to malfunction due to potential differences between the various control devices and signal reflections from the 485 bus. The contractor adopted a 485 sharing device from Shenzhen Tiandi Huajie Technology Co., Ltd., connecting the 485 lines of multiple control devices to the input ports of the 485 sharing device, allowing them to share a single 485 output port. Because the input ports of the 485 sharing device are opto-isolated and use independent drivers, the potential difference and signal reflection problems are effectively solved. This allows multiple matrix switchers, DVRs, and control keyboards to coexist in a single monitoring system. A related diagram is shown below: