Signal Transmission Devices Review. Prt.3 Crossover cable

The concept of signal transmission by crossover cable consists in asymmetrical signal to symmetrical one transformation and bidirectional signal transmitting.

The symmetrical transmission method consists in equalization equipment installation at the receiving site. This receiver modifies an asymmetric signal into symmetric one, that allows to increase the noise security level during the transmission of a few different signal types by one multi-pair cable. For example, audio and video signals transmitting, telephony, etc. Opposite to coaxial cable, in crossover cables the external electromagnetic noise effects on both conductors at the same time. As is well known, the received signal is antipodal, and the interference is inphase, that is why the interference is automatically suppressed by a signal booster, which is equipped with differential input. It stands to mention, that it is much more cheaper to install and support systems, where multi-pair cable are used, in opposite to similar projects, based on coaxial cables. The labour intensity is much more lower in this case. In addition, the cable system of crossover type is not so cluttered, pawn elements have tinner sectional view, less wiring ducts are needed.

It is possible to create a project with an overcapacity: just leave spare wires in multi-pair and use it as and when necessary. There is a wide variety of TV-signal transfer devices by crossover cable and cross-functional kits, which can conform to every length an type of communication lines. It is necessary to remember, that the unshielded twisted pair is more effective, because the shielded cable is very exposed to the influence of a shield parasitic capacitance, which decrease maximum range of TV-signal transmission in twice.

The most important moment of TV-signal transmission by crossover cables is a fine-tuning of transmitter-receiver equipment, which is the thing the receivable signal quality depends on. A special television signal test-generator, which forms a test card (also known as a test pattern). It helps to adjust the amplitude-frequency characteristic of crossover cable and to remove the frequency distortions.

It is necessary to remember about a built lightning guard while choosing the TV-signal transmitter-receiver equipment. Output stages of transmitting sets and input stages of receiving sets may break down because of electric impulse leakage. That’s why the lightning guard is a necessary factor to avoid permanent repairs of burned-out facility. To tap-off static discharges it is necessary to connect the receiver and transmitter to a ground component, while the grounding system installing.