April 05, 2023

Basic Knowledge Required for Security Monitoring

What is a cloud mirror control decoder?

Answer: A decoder is a device that converts control signal sent from external interface into a voltage signal for pan/tilt and lens control.

What is a coaxial cable?

Answer: The name of a coaxial cable (COARIAL CABLE) is related to its structure. Coaxial cable is also one of most common transmission media used for surveillance. The pair of conductors it uses to transmit information is selected according to structure in which cylindrical outer conductor is installed outside inner conductor (thin strand) and two conductors are separated from each other by insulating materials. center of central axis of main line is on same axis, so it is called a coaxial cable, and impedance is 75 ohms.

What is transmission distance of a coaxial cable?

Answer: According to basic requirements of PAL-D video distortion in my country, measured transmission line value without transmission distance compensation is: 75-7 coaxial cable is about 200-250m, 75-5 is about 100-150m.

What are characteristics of a coaxial cable?

Answer: Consumer coaxial cables have specifications SYV75-3, SYV75-5, SYV75-7, SYV75-9 and others.

What is twisted-pair transmission?

Answer: Twisted Pair (TP: Twisted Pairwire) is most commonly used transmission medium in integrated wiring. A twisted pair cable consists of two insulated copper conductors. Twisting two insulated copper wires with each other with a certain density can reduce degree of signal interference, and radio waves emitted by each wire during transmission will be canceled out by radio waves emitted by other wire. Twisted pair usually consists of two insulated copper wires 22-26 mm wound around each other. Its characteristic impedance is about 100 ohms, and distributed capacitance is about 15 pF/m. Unlike coaxial cables, signals are transmitted in a balanced way over twisted pairs. When using video over twisted pair equipment and twisted pairs, this can be guaranteed in video signals high quality can be transmitted over a distance of up to 1.5 km.

What is IP video surveillance?

Answer: IP is an abbreviation for Internet Protocol, which is one of most commonly used protocols for communication in computer networks. The solution for IP monitoring is to transmit video information in digital form through a wired or wireless IP network. As long as network can reach site, video surveillance and recording can be done, and this monitoring can also be perfectly combined with many other types of systems..

What is a video amplifier?

Answer: Video Amplifier When video transmission distance is relatively long, it is best to use a larger diameter video cable. At same time, a video amplifier can be added to line to enhance signal strength to achieve purpose of long-distance transmission. The video amplifier can enhance luminance, chrominance and synchronous signal of video, but interference signal in line will also be amplified. In addition, too many video amplifiers should not be connected in series in circuit, otherwise image will saturate and distort.

What is RS-232 serial interface standard?

Answer: RS-232 is most widely used serial interface in PC and communications industry. RS-232 is defined as an unbalanced standard for extending range of low speed serial communications. RS-232 uses an unbalanced transmission method, which is so-called single-ended communication.

What is RS-422 interface standard?

Answer: RS-422, RS-485, data signal uses differential transmission mode, also called balanced transmission. The full name of RS-422 standard is "Electrical Characteristics of Balanced Voltage Digital Interface Circuits", which defines characteristics of interface circuit. The 4-wire RS-422 interface actually has a signal ground wire, 5 wires in total. The maximum transmission distance is 4000 feet (about 1219 meters) and maximum transmission rate is 10 Mbps. The length of a balanced twisted pair is inversely proportional to transmission speed, and maximum transmission distance can only be achieved at speeds below 100 kbps. The highest data rates are only available over very short distances.

Typically, maximum data transfer rate over a 100-meter twisted-pair cable is only 1 Mbps. RS-422 requires a terminating resistor whose resistance value is approximately equal to characteristic impedance of transmission cable. There is no need for a terminating resistor when transmitting over an instantaneous distance, that is, as a rule, a terminating resistor is not required at a distance of less than 300 meters. A terminating resistor is connected to farthest end of transmission cable.

What is RS-485 interface standard?

Answer: RS-485 is developed from RS-422, so many electrical rules of RS-485 are similar to RS-422. If balanced transmission mode is used, a terminating resistor must be connected to transmission line. RS-485 can work in two-wire and four-wire modes, and a two-wire system can realize true multipoint two-way communication.

The difference between RS-485 and RS-422 is that their common-mode output voltage is different, RS-485 is -7V to +12V while RS-422 is -7V to +7 V, RS- The minimum input impedance of 485 receiver is 12 kΩ, and RS-422- 4 kOhm; RS-485 complies with all RS-422 specifications, so RS-485 drivers can be used in RS-422 network applications.

What are similarities and differences between RS-422 and RS-485?

Answer: RS-422, RS-485, data signal uses differential transmission mode, also called balanced transmission. Four-wire RS-422 interface. In fact, there is also a signal ground wire, 5 wires in total.

RS-485 uses two-wire mode, which can realize true multipoint two-way communication. The difference between RS-485 and RS-422 is that their common-mode output voltage is different,

What is a video switcher?

Answer: The video switcher is a key device on main console in control center for selecting video signals. Simply put, multiple video signals are input, and by controlling them, one of video signals is selected for output. In a telemonitoring system consisting of several cameras, it is usually not necessary to use monitors with same number of cameras to display image signals of each camera in a one-to-one correspondence.

What is a multi-view controller?

Answer: Using image compression and digital processing techniques, multiple images are compressed on monitor screen according to same ratio. Some of them also have a built-in sequential switching function, which can display full-screen images from each camera sequentially and at certain intervals on monitor in turn (same as switching host computer to switch images in turn), and can be used with VCR as described above. Sequence and time intervals are recorded.

The time interval is generally adjustable, with sequence switching, picture-in-picture, multi-screen playback image display, interconnected camera alarm display, pause touch screen, alarm recording playback, time, date, title display, etc. Function.

What is a video separator? VDA (Video Distribution Amplifier)

Answer: The distributor is most commonly used component of distribution network of a cable television transmission system and is used to distribute signal. Its function is to equally divide one input into multiple outputs, usually with two distributions, three distributions, four distributions, six distributions, etc.

What is video switching control?

Answer: The matrix system CPU controls video switching from all camera inputs and monitor outputs. Switching can be controlled by keyboard, system switching queue execution, automatic alarm response function, etc.

What are methods of switching systemss matrix system?

Answer: Matrix system switching can be divided into five system switching methods: free switching, program switching, synchronous switching, group switching and alarm switching.

What is a free-switchable matrix system?

Answer: A free switching queue is a group of camera inputs programmed to cycle through monitor. The image from each camera can be saved for a different time, and each monitor has an independent switching queue.

What is software switching in a matrix system?

Answer: Multiple queues are sent to any monitor at any time by an agent or timed calls. Each switching queue can consist of several cameras and their preset points, delay times and additional switching actions. In a switching group, same camera image or several auxiliary camera actions can appear multiple times.