Extending Surveillance Monitor Signal / Cable RunsBy Ethan Ace, Published Aug 09, 2011, 08:00pm EDT
Often surveillance monitors are located quite some distance from VMS workstations. Since most video signals have relatively modest default distance limitations, care must be taken to ensure against video degradation or signal loss. In these cases, you will need to choose the best method to extend the video signal. In this note, we look at the advantages and disadvantages of using longer cables, line drivers, pre-terminated runners and UTP extenders.
Types of Signal
First determine the type of signal being sent from the workstation to monitor. There are fundamentally two main options: analog and digital.
- For PC video, analog includes composite and VGA.
- Digital includes HDMI and DVI.
Today, most monitors are high-resolution, typically 720p or 1080p if using widescreen displays, or 1280x1024 or 1600x1200 if using 4:3 displays. When using displays capable of these resolutions, there will be noticeable quality differences in clarity and color trueness between VGA and digital display technologies. This does not mean that VGA is unusable, simply that for very large and critical displays, digital is preferable.
Being analog, VGA suffers from different issues at long lengths than digital signals. VGA may suffer from color loss, white balance issues, and intermittant issues. Digital signals, however, are more likely to simply work or not work. Users with digital cable or satellite may also notice this difference versus analog cable signal.
Max Distance: The maximum distance any of the signals should be run without amplification or active equipment varies depending on the desired resolution, technology used, and the quality of the cable. However, there are some rules of thumb.
- VGA can typically be run about 75' or more before requiring some sort of amplification.
- DVI, on the other hand, should be run a maximum of 25' before amplifying.
- HDMI cables beyond 45' are typically not tested and certified to be compliant to the HDMI spec, but will work fine in many applications.
In all cases, buying quality cables produces better results than no-name brands.
The simplest way to extend any of the above video signals is to simply purchase and install a longer cable. This provides some challenges, however. Connectorized VGA and DVI cables are not easy to pull through walls and ceilings due to the size of the connector. VGA "install" cables are available which require the installer to connectorize one end of the cable in the field, but this is a time-consuming process, and may be hard to perform and troubleshoot for inexperienced technicians. Some manufacturers provide screw-terminal wallplates and connectors to remedy this issue, however. Cables can be found online for very little, as low as $20-25, which may be fine for shorter lengths of ten to fifteen feet. Users should expect to pay $100-200 for a quality 50' cable, however.
When installing cables longer than the maximum recommended distance, a line driver is recommended. These units install in line with the video cable and boost the output signal, so that signals may be carried further than normal. As with cables, buying from a reputable manufacturer (such as Extron or Kramer) is recommended. Inexpensive units sometimes do not pass all data on the cable, resulting in monitor blanking or incompatibilities. Line drivers are available for VGA, DVI, and HDMI. Line drivers will typically run between $100-150.
A new development in the past couple of years, products such as RapidRun and Hubbell's X-END allow simpler installation of video signals. These products utilize pre-terminated runner cables with plug-and-play ends in both wallplate and pigtail form factors. This makes the cable easier to pull through walls, conduits, and ceilings, and doesn't require any special tools or skills to terminate, unlike multi-pin connectors. The downside to this is additional cost, as systems such as these typically cost more than simply purchasing longer video cables. Efficiencies in installation may make up the difference, depending on the installation environment. A complete system including all components (runner cable, wallplate(s), and/or lead cable(s)) can be found online for $100-200, depending on configuration.
The final method for extending video signals is to use UTP converters. These devices are available in both active and passive versions, with active versions usually allowing for greater distance and options such as equalization and skew adjustment which may be needed for longer runs. Typically, UTP extenders require two Cat 5e or 6 cables; Cat 6 typically provides greater distance and resolution, with some units even requiring shielded Cat 6 for long-distance HDMI runs. The two biggest advantages of extending video over UTP are simplicity of installation, since only RJ-45 terminations need be performed, and obviously, the increased distance over typical cables. It can at times become bothersome to find a location for the transmit and receive units, but manufacturers have begun fitting the units into wallplate form factors to alleviate this issue somewhat. UTP extenders vary in price, depending on the manufacturer and the signal type, but typically can be found online for $150-250.
While all of the above methods are possible, we have two key recommendations:
- Extend signal via UTP wherever possible. Simply put, its advantages in termination simplicity, and use of low-cost readily-available cable make it the simplest for security integrators to implement. Normally, these units are plug-and-play and require little set up as well.
- Use the highest-quality interface available. If available, we recommend using at least DVI, if not HDMI. The quality gains may very well be minimal, depending on the application, but since equipment to extend any of these signals is so similarly priced, it makes more sense to use the digital interfaces wherever possible.
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