Physical media

Them means physical or guided are those transmissions from telecommunications wired, well with thread conductor and their types or fiber optic. The first can be divided into two types as they shielded coaxial cable or do not like a normal phone. There are wired with or without screen for almost any application not only the typical coaxial, so for example a UTP cable (for LANs) can be with or without screen being the second best to avoid interference, say that the "screen" is a metal which has cable and grounded coating (sometimes is the negative or common) and avoids cause electromagnetic interference noise inside.

RS-232

Is used for communications between a terminal and a peripheral, them old ports series were more or less based in this standard the data can travel in two senses simultaneously. Minimum communication consists of three cables, TX and RX (send and receive) and the dough or GND. Between the two machines RX one connects to the TX of the other and vice versa and the GND common, is used for distances up to 15 m short

Connector RS-232
Connector RS-232

 

RS-422

It is the extension of the RS-232 to the industry, basically is the same system but using a slightly different physical system. While the RS-232 using a voltage in relation to the Earth, the RS-422 carries its own cable to measure the potential difference, this difference allows wired up to 1200 meters front the 50 or 60 of the former.

Connection of the RS-422
Connection of the RS-422

RS-485

Advancing slowly to take advantage of the same wiring for different components and very www.solanacenter.org to the protocol MODBUS this wiring is it version multipoint of the RS-422, i.e., the former only us serves to communicate two machines and with the RS-485 can join many more with system esclavo-servidor. Connection is now slightly different, are a common GND for everyone and usually the shielding, then we have two cables the A + and B + equally common for all devices, at the end of the connection has put a resistance of 120Ω and 0. 25W. A machine is the master and this sends requests to each device and it will respond. The following image shows a PC connected to several elements, to say that the PC has an RS-232 port so it has an adapter for RS-485.

A RS-485 connection
A RS-485 connection

USB

By all known USB is the improvement of the previous (similar to RS-232) serial port, it is a standard peripheral connection only USB connection allows us to connect a device each time, if we need several elements may use a hub, but each device will have its own cable and connection and only one for each cable.

Different USB connectors
Different USB connectors

 

ETHERNET

It is the IEEE_802.3 standard generally used two- or four-wire twisted pair (also with coaxial or fiber optic) used for distances up to 100 meters, allows tree, bus and ring topologies. They are multicast channels, i.e. all machines they listen to messages but they ignore those who are not destined to them although there are intelligent routers which "deviate" each package by the a way to avoid saturating the rest lines.

Typical cable to ethernet connections.
Typical cable to Ethernet connections.

Ethernet/IP

The industry tends to be a place where there are risks of different nature, fire, interference electromagnetic, humidity… by this building is in the standard Ethernet and combined with the Common Industrial Protocol (CIP). Why the switch or the wiring must be designed for hostile environments.

Coaxial cable

Known by all to be wiring antenna reception and arriving to our televisions, it is often used in almost any installation of cameras for CCTV, but also for computer communications. He positive and the information circulates by the inside of the cable the shielding is the negative and the common (negative or mass), usually is usually connect both ends of the screen to Earth, this metal "absorbs" them waves electromagnetic that can produce interference and noise in our signal and them force to go to Earth, by what improves our communications , there are various types of wiring standard coaxial better or worse quality according to its dielectric (insulation between the outer maya and central thread) and its thickness, tend to use one or the other depending on the distance.

 

X-ray of a coaxial.
X-ray of a coaxial.

 

Fiber optics

The best means of transmission, the more rapid and reliable is the fiber optic, is basically a cable where flows (visible or usually ultraviolet) light, explained roughly would be as if the Interior fiberglass walls were mirrors where light bounces. Not being a current flowing if interior does not produce interferences if this close to sources of electromagnetic fields as with normal wiring. Its only drawback the high price, also the complication for the joints being expensive and made by very skilled people.

Fiber optic
Fiber optic

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