Desórdenes Músculo Esqueléticos

An ongoing debate rages about how the IP camera cables should be terminated.

This argument surrounds two common options:

 'Direct Attached', where the first terminates the field cabling with an RJ45 modular plug, and connects it directly to the camera.

 'Jack & Patch': where the cables are first terminated to a jack or patch panel, and then connected to security devices by patch cord. In this note, we explain the options, tradeoffs, and elaborate on the pros and cons of each method.

The Two Methods

Direct Attach Method: The most common method of attaching devices to a network is simply plugging each terminated end into a device. Cables are run directly to a switch and to a camera or controller in the field, using an RJ45 modular plug at both ends of the cable. Testing is performed from these plugs across the length of the single cable.

However, many cite a second more permanent method is better despite being more complex:

Jack and Patch Approach: According to the 12th Edition ofBICSI's

TDMMand prior, all horizontal cabling should be terminated in the closet end on a patch panel, and in the field, on a jack. Starting in later editions, this requirement was relaxed for security equipment and other installations where accessibility may be difficult or tampering may be a risk.

Connections are made from the patch panel to switch, and from the jack to device with patch cords. The resulting section of cable from patch panel to jack is called the 'permanent link'. Typically jacks are installed in a wallplate for interior cameras, and patch from the plate to the camera. In exterior applications, jacks are commonly mounted in junction boxes.

IPVM 105 The Heart Of The Debate

The major issue driving this debate is the 'modified permanent link' which modular plugs create. Since cables are specified by standards to be

terminated in the typical link fashion, testers were created to test the normal permanent link, resulting in not-quite-accurate tests when testing through a modular plug. How inaccurate these results are is debatable, and in practical terms, negligible.

Building automation systems have used the direct attach method for years, as it was recognized by TIA standards that in some cases a jack and patch cable are impractical or unserviceable. Current Editions of BICSI'sElectronic Safety and Security design referencehave come to the same conclusion. However, it should be noted that security applications break other

fundamental rules of BISCI standards, such as each outlet being mounted 18" above finished floor with two cables run to it. Security devices, just like BAS devices, are application-specific, and different standards apply while respecting original intent where possible.

While, practically speaking, there is nothing wrong with either of these methods, and much is left up to preference, directly attaching plugs is generally preferred by the majority of integrators. There are two main drawbacks which may be a problem when using this method:

 Cable flexibility: In UTP cable used for horizontal runs, each of the eight conductors (four pairs) is made from a solid copper conductor. In patch cables, each conductor is made up of multiple thin copper strands. This makes the conductor, and in turn, the entire cable, more flexible. For this reason, patch cables may be able to fit into tight domes where sharp bends are without straining or pinching the cable where solid conductor cable would have issues. Strictly

speaking, however, according to standards, bend radius is four times the diameter of the cable, regardless of solid or stranded

construction.

 Modular plug construction: While Cat 5e cable is almost always 24 AWG, some manufacturers of Cat 6 and higher cables have sized conductors up to 23 AWG. Care should be taken when selecting cable/modular plug combinations, to make sure the plug will handle larger-gauge wire, or it may not work properly, or simply not at all. Users should be aware of challenges in specific applications, as well:

 Interior cameras: When installing interior cameras, the key

consideration is where the camera will be mounted. If the cameras are to be wall-mounted, or in the case of warehouse or other open-ceiling environments, installing jacks is simple, either in a surface-mount or recessed box with wallplate. When using ceiling-mounted domes, however, installation is trickier. As

IPVM 107 discussed in our installation issues update, exposed connections are not allowed by code above drop ceilings. This means that, unless the dome has room enough to install a jack inside it (which is unlikely), a junction box must be provided to house the connections, making the direct attach method much simpler.

 Exterior cameras: Using jacks in exterior locations can be much trickier than their interior counterparts. If using box cameras, a jack may be located in the housing. However, exterior domes are as unlikely as their interior counterparts to have enough space to locate a jack and patch cable. If an enclosure is provided, for surge

protection, wireless equipment, or other needs, the jack may be located there. In most cases, however, the direct attach method will be simpler.

No matter which method is used, care must be taken during installation. Maximum cable pulling tension and not exceeding bend radii should be observed. All components should be Cat 5e or Cat 6 rated, including mod plug and patch cables. If all of these are followed, connections should experience few issues.