Ethernet network connection on one pair

It is known that 10/100base-T works on two pairs. On the first reception, on the second transfer. Beautifully, logically, allows full-duplex. Thus all remember that the coaxial manages in only one pair conductors. Strangely enough, it does not cause an internal contradiction. And in vain.

These two essences are connected (if not to go into subtleties) at level of AUI which is absolutely identical to both ways of data transmission.

Standard circuit of the coaxial adapter.

If a little to think over half-duplex work in a mode a point-to-point, there is the following thought: really the central chip is so silly, what will conduct transfer at the same time with reception? No, on it his logicians should suffice. Means, it is possible to disconnect the detector of collisions, after all crossing of packages can arise only at the simultaneous beginning of transfer by both points adjusted for time of distribution of a signal.

The probability of this event is rather small, and the undemanding user can leave with quiet soul conflict dismantlings on a share of protocols of higher level. In summary to have. work of ethernet on one pair.

In consciousness there is the simplest circuit of work.

The simplest circuit of work of ethernet on two wires.

It is necessary to tell at once what exactly this decision was not checked, and in practice most likely, some completions be required. It is better to perceive this circuit as concept demonstration, instead of the guide to action.

Thought it not the new. Sent it together with the materials Sergey Malcev ([email protected]). Its today's development goes slightly further, and the decision many years ago embodied in iron, functions still.

Here is how the modifed ethernet-card looks. Anything especially terrible on it it is not visible.

The author of completions could not be limited small therefore on the network adapter it is made additional грозозащита and "dalnoboynost" is increased.

Here real circuit of alterations. Treats the type of the card shown above, and does not apply for absolute universality.

The circuit of alteration of ethernet of the card for work on two wires.

Diodes in the middle of drawing - in fact standard грозозашита. Anything special does not differ, only it is established in an unusual place. КС175, shown on the right, serves the same purposes.

Here is how it looks "in real".

The element F shown on the circuit - the fuse. Why the same is made exactly so, for me a riddle. I so have a suspicion what exactly such element appeared at the right time near at hand.

The condenser C is urged to fight from a constant component which can appear at such alteration. The resistors shown at the left, apparently, coordinate loading. Why it is made exactly so, instead of differently - a question to the author of the circuit.

And the last alteration - increase in range of work. Really, on usual distances nevertheless it is simpler to lay a normal cable and to change nothing in the circuit. And here when there is one pair on communications.

Such options seldom keep within 100 meters. Big luck when 300-500 meters will turn out. Then at the midget budget it is possible to try the described decision.

It becomes the quartz resoldering. The result is shown in the photo.

What turned out as a result? The device, cпособное to give out at connection a point-to-point of 5 megabits on 300-500 meters on a usual cable, and to 1 kilometer on special, the P-296 type. If necessary to increase distance it is possible to try to lower even speed.

Under condition of almost "zero" price, such decision can compete in certain cases both with HomePNA 1,0, and with Granchami.

By the way, some suspicions - whether here start to creep in value of the invention of HomePNA, whether and so strongly its first version differs from ethernet'а so is great. As it would be desirable to learn, how Granchi (SBNI 12-02) from Arkneta who well works on one pair far left, and can be slowed down" by quartz change till absolutely low speeds. And in general, whether producers make a fool of us beautiful names, giving out cheap and simple "improvement" for the epoch-making event lifting стоимосоть of the equipment in tens (or even hundreds) time. What to do? And whether the industrial answer to an arbitrariness is possible rather cheap, but nevertheless? It turned out after all with грозозащитами (ProtectNet) to reduce ARS sales to the level close to zero. Ethernet is not much more difficult.

Author: Sergey Malcev
Source: http://nag.ru/