Distributed matrix systems: development prospects.
Despite the growing interest of the video surveillance market in digital network technologies, analog solutions based on programmable matrix switches are still relevant. Manufacturers of analog switches report a constant increase in sales of these devices. Of course, this growth is primarily due to the general trend — an increase in the volume of the market for technical security equipment. However, matrix switches do have their own consumer and their own area of application. Switches are a characteristic element of video surveillance systems in large shopping centers, stadiums, train stations, as well as enterprises where, in addition to security functions, there is a need for technological surveillance.
Features and capabilities
Matrix switches are complex and expensive devices based on a specialized computer. Switching incoming signals from TV cameras to multiple outputs connected to monitors (hence the term matrix), switches do not form multi-screens and do not record. Therefore, for many adherents of modern digital systems, they are completely useless devices. «The customer wants to see everything» — this is often a dogma and the main criterion when choosing a multi-channel video recorder as a solution. Many cameras — more video recorders. Of course, the operator will not look at screens with 16 small pictures, but there is a recording and no event will be missed. These words make sense, but there are objects and tasks that require not only event logging, but also well-thought-out video security. A programmable switch allows you to create a real video patrol of the object. Images from certain TV cameras can be displayed on monitors according to a schedule or events. Indeed, the operator observes the image from only a few cameras, but precisely from those that are currently the most important. Sequentially viewing images from cameras installed on the perimeter of the facility, the operator performs a video tour, as if he were physically present at the facility. Of course, all video signals are duplicated on the video recorder, where the recording is made. Such a system is more functional and increases the level of security of the facility. The switch literally makes the operator work — the change of images when switching involuntarily attracts attention. The most important area of observation is constantly displayed on the same screen, and the operator is always aware of events. An important advantage of using switches as part of the security system of the facility is their effective integration with access control and fire alarm subsystems. Programmable switches often have alarm input blocks and relays, through which integration can be carried out at a simple hardware level. Alarm processing, i.e. displaying images on the operator's screens, can include switching cameras in a cascade or salvo, when images of several segments of the perimeter or an entire floor of the building appear on several monitors. Integration can also be done at the software level. This feature is available in almost all switches thanks to the RS-232 port.
Architecture of switches and systems based on them
The architecture of programmable matrix switches consists of a central processor with a control program, video signal switching units and additional peripheral units. In the simplest models, all units can be combined in one case. In more capacious and expensive models, the units are independent and connected via one of the common interfaces — RS-422/485. Additional units can be used for connecting alarms, executive relays, video signal receivers via twisted pair, external ports, emergency switches, etc.Such switches allow creating distributed systems for various objects. We are talking about the possibility of distributing video signal switching units at the facility. For example, a system of a high-rise building or a plant with several production workshops. Laying a cable from each camera to the surveillance center is often impossible here due to the physical limitations of cable shafts. Using a switch consisting of several switching units, it is possible to locally connect television cameras (floor, workshop) to the units, placing them within the floor or one of the workshops. In turn, each unit is connected via RS-422 (twisted pair) to the central processor installed at the main post, and is controlled by it. Thus, one control cable and several video cables from the monitor outputs are laid from each switching unit. Operators have access to any camera in the system, while the system is more economically attractive.
A number of programmable matrix switch manufacturers offer solutions using satellite switching units. These devices are actually full-fledged programmable video switches of small capacity. They can be used as autonomous video signal control systems at one of the sites of a large distributed site, and at the same time they can be integrated into the software of the central processor of a large matrix switch, connecting to it via the same RS-485 interface. As a result, it is possible to create a system with a central database and events, including several independent systems with independent databases and events.
Development Prospects
Programmable matrix switches evolve, acquiring capabilities typical of digital systems or integrating with them. Thus, modern video switches have the ability to be configured and controlled remotely via Ethernet. Thus, any distance restrictions actually disappear and integration with other security subsystems is simplified.
Many switches can be part of large distributed IP systems. IP decoders are connected to switching units via video signal and the central processor via RS-422. By decoding IP streams from network recorders, we receive signals at the switch input. By controlling the decoder via the central processor program, the operator works with the archive of the remote NVR, requesting a particular video stream. Such systems are in demand where delays in image transmission are unacceptable (which is typical for IP systems) and high quality of live images without digitization and compression is required.
In general, solutions based on programmable matrix switches remain in demand in the environment of professional systems and complex tasks.