We get rid of “unnecessary” equipment
The cable system of small offices, as a rule, has only a horizontal subsystem SCS, since the office itself is usually located on one floor. Standards provide for the horizontal subsystem SCS the presence of floor cross. Horizontal cables diverge from floor crossings to workplace outlets. Recently, in almost all newly installed office networks, Fast Ethernet 100Base TX technology has been used, which places high demands on the parameters of the cable system. Connecting active network equipment to the cross and sockets of workplaces should be carried out using patch cords. Horizontal lines and patch cords are made of different cables. Twisted pairs of horizontal cables are made as single-core, from monolithic copper conductors, and twisted pairs of patch cords are made of stranded wire – to give the cable more flexibility and resistance to mechanical stress. The actual cross-section is one or more patch panels mounted in 19-inch racks or cabinets. Manufacturers produce patch panels with a different number of installed sockets of RJ-45 modular connectors (ports); usually their number ranges from 12 to 48, and in height they occupy one or two standard seats – a unit (1 unit = 13/4 “). A small hinged 19-inch cabinet, patch panel and patch cords make up a fairly significant part of the cost of a LAN a small office (Fig. 2). To reduce these costs, manufacturers offer a special 10-inch version of the cross for networks for 8 … 12 jobs, which is 2 … 3 times cheaper than the 19-inch one. Already better, but that’s it It’s still expensive. Is it possible to do without cross-country at all? In practice, usually Tupa.
Eight-pin RJ-45 plugs are installed on the ends of the cables that must be plugged into the modular sockets of the patch panel and directly connect them to the sockets of the active equipment. The other ends of horizontal cables are plugged into outlets at workplaces. It would seem that it is a working solution for a small network. There is some logic in this: indeed, why do we need cross in a small network if few employees sit in their places and do not move from place to place, and the cable telephone subsystem already exists and is not linked to the LAN cable system?
However, there is a certain degree of risk in such a decision. The fact is that the plugs of modular connectors of the RJ-45 type are designed specifically for installation on cables designed for patch cords that use multicore conductors. Knife contact petals during crimping the plug easily enter the body of the conductor and provide reliable contact. Another thing is when the plug is installed on a horizontal cable using monolithic single-core conductors. Petals can break when crimped, resting on the solid body of the conductor, or go tangential to it. As a result, the contact in the plug is unreliable. In order to reliably mount the plug on a horizontal cable, it is necessary to use a plug with a special shape of contact petals, which are rounded with two teeth at the ends or a plug with a universal design of contact petals.
Some installers in their innovative impulse go even further – refuse to use sockets and terminal patch cords at workplaces and connect the system board network board in the manner described above, i.e. directly. This is not worth doing, at least when it comes to horizontal cable. The fact is that in the user’s working area the length of cable that goes to the network card of the system unit is subjected to increased mechanical stress: shock, tension and twisting. In addition, unreliable contact in the plug is possible. All this affects the electrical characteristics of the cable in the area of the system unit and can cause unstable operation of the network. If we apply such a connection scheme, then for these purposes it is better to use a multi-core crossover cable. It should be remembered that this cable has poorer electrical characteristics than horizontal, so the length of such a line is not recommended to be made more than 20 m. Cable for cords is about 2 times more expensive than horizontal cable. However, given that such organization of the cable system saves money on cross equipment and sockets, this solution is economically feasible, especially for combining 5 … 8 workstations located in one or adjacent rooms.