tod 9010

tods5eshoes · Wysłany: Pon 18:16, 07 Mar 2011 Temat postu: tod 9010

Proven Systems For Designing An IP Camera System by Terry Stanfield
Hard Knock lessons from a vet of CCTV systems large and tiny
When you're looking at coming up with an IP camera system normal rules for wiring the cameras and recording the cameras go out the window. Below I have listed 3 design traits that have changed from conventional coaxial-based camera systems to IP based camera systems.
Rule 1: Infrastructure Design
a couple of years back I was presented with a large camera system that required over ninety cameras in a building that was over 750, 000 square ft. The challenge,[link widoczny dla zalogowanych], using traditional camera design, was wiring each camera back to a central location where the command console was located. In some instances, camera locations were over 1, 500ft from the command center. Since coaxial wires limitation for RG59 and RG6 wire are between eight hundred and 1000ft, solving the distance limitation problem was critical. Using the methods available to me at the time, I had a choice between fiber optic wire or UTP ( unshielded twisted pair ) wire. Although fiber optics generally will produce a clearer picture with less distortion, it was cost prohibitive for the project. I chose UTP wire and with an active receiver at the command console and passive transmitter at the camera. This provided for wire runs of at least 3000ft. UTP wire is just CAT3 or CAT5 cable ( commonly known as Ethernet wire ), which is employed for telephone and data networks. One of the 4 pairs of wires sends video down the wire. The twisting of the wire provides its unique benefits. This gives the cable its name of unshielded twisted pair. At the time, now more than four years ago, this was the best answer for the application because it met the criteria for transmitting the video and met the client's budget.
IP Video changes everything.
Using IP cameras presents a completely new set of rules for transmitting video. Where before we managed to transmit a video signal up to 1000ft using coaxial wire we are now limited to only 300ft or one hundred meters. Initially, this may appear to be a downside. To anyone that is acquainted with designing a computer network it is apparent that this layout is really a benefit. Imagine the application below:
You have five cameras you would like installed. They're all located along a back wall of the building looking out to the shipping and receiving area. The recorder is found at the front of the building in an IT closet. Under conventional video design, all five cameras would have a coaxial wire installed from the camera to the recorder. In this example, let's say the distance is a mean of 500ft from the recorder to a camera. 5 cameras at 500ft each would require 2, 500ft of coaxial wire. Using a network solution the following wiring would be required. A single wire, typically fiber,[link widoczny dla zalogowanych], would be pulled from the front of the building to the back. At every end of the fiber, there would be a termination point. The termination point at the front of the building would be considered the Main Distribution Frame or MDF. The point at the back of the building would be the Intermediate Distribution Frame or IDF. An IDF is defined as a location between the MDF and the end device, in this situation the camera. All of the cameras would be wired to the IDF location. For our example, we will say it's an average of 100ft from each camera to the IDF. We might need 500ft of network wire. Conclusion is that instead of pulling 2500ft of coaxial wire you are installing 500ft of CAT5e wire and 500ft of fiber.
The Big Bonus behind IP Video
The chief benefit behind a network solution is scalability, which leads to serious long, and short term savings. When you have five locations all with five cameras and all 500ft from the recorder, the costs add up quickly with normal systems. In this position the cost savings can actually begin to add up. Going back to our example for a minute, shall we say you need to add a new camera to view the interior shipping door. The infrastructure is already in place. Now all that is's required is pulling a single CAT5e wire from the new camera location to the IDF. Perhaps this is only 50ft away. Using the old design, you would need to tug another 500ft of coaxial wire back to the recorder. This adds up to a wire savings and a big work cost reduction.
Rule 2: PoE - The'Power' of a Single Cable
PoE or Power over Ethernet is just the transmission of power together with information over a standard Ethernet wire. In a Power over Ethernet system,[link widoczny dla zalogowanych], a PoE network switch makes available up to 15Watts of power to the end device. This can be a telephone, camera or any other device that sits on a network and requires less than 15 watts of power. When designing an IP camera system you should look for cameras that use this technology. There are two b[link widoczny dla zalogowanych] benefits when using PoE for your system layout.
Benefit 1: just one wire is critical to each camera for both power and video transmission. Versus a standard camera system that uses a Siamese wire for both video and power. A Siamese wire has a coaxial RG59 wire and sometimes a 18 gauge two conductor wire molded together to form a single wire. This gives the appearance and simplicity of pulling a single cable to each camera. The flaws to Siamese wire compared to CAT5 wire is it is seriously more expressive. Siamese wires contain more copper, which is an expensive commodity in [link widoczny dla zalogowanych]ay's market. Siamese wire is also tougher and burdensome to install.
Benefit 2: No further power supply is necessary for powering the cameras and it simply needs a single termination at the camera and switch location. These two further features lead to the same benefits: cost benefits and a more flexible and scalable system solution. Scalability and space necessities are becoming an increasing concern for many IT departments. When adding a network camera system the potential rack space needed for the present as well as future can be extremely critical when coming up with a system. Using PoE can save space and reduce heavy, rigid bundles of wires.
Rule 3: Centralized or Edge Recording
There is no right or wrong when it comes to using edge recording or centralized recording. A majority of your call will depend upon your own application and existing network infrastructure. A half-breed of the two styles might be the best solution but this can add extra cost and restrict your available camera options. In a meeting with a s[link widoczny dla zalogowanych]l district, I was questioned about which solution was better. I responded that I felt neither was a better solution; both solutions have their benefits and it depends on the application. During my meeting I described the following advantages and drawbacks of each.
Centralized Recording:
Imagine you've a company that has five buildings ranging in size between ten thousand to 50, 000 square ft. All five of your buildings are found within a large economic park. Each building has a controlled number of fiber optic wires between them. Your company has a main server room found in the biggest of the five buildings. The IT department manages the server room and there is limited restricted access to that room. The remaining four buildings are accessible thru fiber from the server room.
For this example, centralized recording offers you the most cost-effective and scalable solution. Centralized recording works well here. There's a main server room and all of the buildings are connected thru locally run fiber. Employing a single recording location is inexpensive because all of the recorded video is stored at a central location. A single server as against five servers ( if using edge recording ) will record the video,[link widoczny dla zalogowanych], leading to a big savings. In each building, PoE network switches would connect to the cameras. The fiber optic wire would broadcast the video back to the central server room for recording. This solution is also awfully scalable. Adding a camera to any location within the five buildings is as simple as connecting a camera to the closest PoE switch. In this actual application, centralized recording fits best because of the environment and infrastructure available. A drawback of centralized recording is if a fiber is cut between any one of the buildings and the server, all of the cameras within that building will no longer be recorded or be ready to be viewed live. In this example, all of the video from these cameras will be lost.
Edge Recording:
In this example, you have a corporate office building and a manufacturing plant. The two buildings are found about one mile apart from one another. You have a dedicated T1 connection between the two locations. The T1 is used to share information transmission between the two sites. Almost all of the installed cameras will be at the producing plant so that corporate is in a position to monitor the plant remotely. The corporate office will have four to six cameras installed to view the main entrance and worker parking area.
For this example, edge recording offers the most cheap solution for your company. Limited connectivity between the two locations is the most important obstruction. The standard IP camera needs about 2Mb per second available bandwidth. The first camera would consume all of the available bandwidth of a T1 connection making centralized recording very unlikely. Edge recording doesn't prevent centralized viewing it only stops the recording of the camera centrally. For this example, you would use two network video recorders. You would scale each recorder to fit the quantity of cameras they'll be recording. From the client side or remote connection, you'd be able to configure the system as though it were a single connection. The sole difference would be the refresh speed of the remote cameras. In this example, edge recording supplies the most cheap answer while still meeting the goals of your company. The downside, in this application, is the price of having two servers and slower live display rates of the cameras.
The Rule Summary:
By reading this, I'm hoping that you are able to see how IP video offers a completely different design and new features that weren't possible or cost prohibitive with a standard coaxial wire system. There are many other benefits when using IP video. The 3 listed above are only some of the benefits that IP video technology has made available to the safety industry..
Topics related articles：

[link widoczny dla zalogowanych]

[link widoczny dla zalogowanych]

[link widoczny dla zalogowanych]