# Design a simple twisted pair cable tester

At the moment, I am an applicant, and since people are born 94 in Ukraine, it turned out to be small, many departments of universities carried out small “scientific” work with students in grades 10-11. I was lucky to become a participant in such work. I got to the fact. TKVT KHNURE, namely to the senior teacher Malinin A.P.
I was asked to create a simple cable tester, the process of creating which I will try to describe in this article.

My task was to create a simple device that allows testing UTP category 5 cable (can be implemented for any cable on a twisted pair cable), which is able to diagnose these types of errors:

- breaks;
- short circuits;
- coup coup;
- crossing pairs;
I left the pair splitting diagnostics to senior students, because with such an error the physical connection remains, and the interference resistance changes (it seems like a tone generator is needed, but I didn’t really go into it - it's too difficult for me).

The device itself consists of 2 parts (let's call them passive and active).
Logical diagram of the device:

So the task of the active part of the tester is to distribute the pulses physically and in time.
Tobish at the outputs of the counter (A1, A1, A3, A4) should look like this:

A1 1 0 0 0
A1 0 1 0 0
A3 0 0 1 0
A4 0 0 0 1

Each pulse will “run” along its own pair, and if there are no breaks and the cable is crimped correctly on the "passive" part, the green LEDs will light up in turn.

What will happen if there are errors in crimping or cable breaks?

Breaks, short circuits : all or several LEDs do not light up, since the circuit is not closed and the current simply does not flow.

Coupling : a red diode will turn on (the color naturally does not matter, but I did not invent a bicycle), since the current will flow in the other direction (not x1> x2, a x2> x1), which will lead to the ignition of a non-green diode.

Intersections of pairs : LEDs on the “passive” part will not light up in turn.

Of course, this device is far from ideal, but still better than a simple "dialers". Unfortunately, I don’t have the opportunity to place photos, I’ll just say that for the price the tester turned out to be 2 times cheaper than the cheapest Chinese counterparts, despite the fact that not very decent people trade on the Kharkov radio market = (
The tester itself was implemented on the installation, 3 microcircuits (inverter, counter , decoder), 8 LEDs, 2 sockets and all sorts of other little things (resistor and capacitor).