Why learn for CAT instead of GATE

Which network cable for video surveillance?

From the surveillance camera to the network recorder, computer or router - this is still the most secure connection for data transmission Network cable. There are many cables available and the abbreviations sound confusing. With PoE the power supply via the data cable is also possible. What is behind the terms and what is important when choosing the right cable?

Network cables, LAN cables, patch cables, Ethernet cables, twisted pair cables?

These terms are often used interchangeably. Basically, this is not entirely correct, but not a problem: network In connection with current computer technology for consumers always means a data network that is based on the Ethernet-Default is working. Such a network is called a local network realized, in short LAN (= Local Area Network). In the LAN, devices such as PCs and surveillance cameras are connected as network clients and exchange data according to the Ethernet standard. If the data is transmitted wirelessly, this is called WLAN (Wireless LAN), and a corresponding cable is required for wired transmission.

The Patch cordis originally a relatively short LAN cable that was only used for the connection between a network client and the nearby junction box or for the interconnection of different connections in more complex systems. In the meantime, however, longer network cables are also known as patch cables.

The designation Twisted pair (TP) refers to the inner workings of the cable: There are a total of eight individual copper wires that are twisted in pairs.

The advantage of twisting: Interferences from electromagnetic fields in the environment (e.g. from power lines) hardly affect the signal quality and the mutual influence of the cores is also reduced.


Shielding: overall shielding and wire pair shielding

The first protection against interference is in one Twisted pair cable already incorporated by the design. In addition, the cable as a whole (overall shielding) and the individual pairs (wire pair shielding) can have a further shielding made of wire mesh and / or coated foil.

The different cable types at a glance:

  • UTP: unshielded twisted pair
    -> There are twisted pairs of wires in the plastic jacket
  • S / UTP: Screened Unshielded Twisted Pair
    -> Plastic sheath, overall shielding made of wire mesh, unshielded wire pairs
  • SF / UTP: Screened Foiled Unshielded Twisted Pair
    -> Overall shielding of wire mesh and foil shielding, wire pairs unshielded
  • U / FTP: Unscreened / Foiled twisted pair cable
    -> plastic sheath, no overall shielding, wire pair shielding made of foil (one or two wire pairs each in a separate shield)
  • S / FTP: Screened / Foiled twisted pair cable
    -> Plastic sheath, overall shielding made of wire mesh, wire pair shielding made of foil
  • SF / FTP: Screened foiled / foiled twisted pair cable
    -> Plastic sheath, overall shielding made of wire mesh and foil shielding, wire pair shielding made of foil

S.always stands for a wire mesh, F. for foil, the information in front of the slash always relates to the overall screen, the following to the wire pair screen.

Category Cat 5, Cat 6, Cat 7

The category, abbreviated to Kat or Cat, is the guaranteed usable for a network cable Transmission frequency designated. In principle, a higher frequency also means a higher maximum data transmission speed - however, the higher the frequency, the lower the maximum cable length at which optimal operation is possible. The relevant categories today are:

  • Cat 5 / Cat 5e: 100 Mbit / s (Fast Ethernet) or 1 Gbit / s (Gigabit Ethernet) - The original Cat 5 was only suitable for Fast Ethernet, the successor Cat 5e for Gigabit Ethernet. Cables that are suitable for Gigabit Ethernet are sometimes referred to as Cat 5 cables. Maximum length unshielded approx. 50 m, shielded 100 m.
  • Cat 6: 10 Gbit / s up to 100 m in length
  • Cat 7:> 10 Gbit / s up to 100 m in length

The maximum speed in a network always determines the slowest component, the cables downward compatible. If you use a Cat 7 cable z. B. on a router that works with a maximum of 1 Gbit, then a maximum of only 1 Gbit / s is achieved.

Power through the network cable - PoE

Where there is no power outlet nearby, Power over Ethernet offers a convenient and elegant way of supplying the surveillance camera with power. All cables are suitable for PoE Cat 5. There are several PoE standards that differ in the power that is available to a supplied device:

  • 802.3at: 15.4 watts of power per port, of which 12.95 watts can be used (PoE)
  • 802.3af: 25.4 watts of power per port, of which 21.90 watts can be used (PoE +)
  • 802.3bt: ~ 90 watts of power, of which ~ 71 watts can be used (PoE ++)

A feeder (power sourcing equipment) is required so that the electricity can also get into the network cable. Inexpensive PoE switches or power injectors take on this role. It is important that the camera as well as the powered device and the feeder use the same standard.

Which network cable should I buy?

For Home usersIf you only want to bridge short distances, an unshielded Cat 5 cable is basically sufficient. The rule of thumb is: as short as possible, as long as necessary. But pre-assembled, high quality Cat 7 cable do not cost much anymore and offer sufficient reserves even if there are sources of interference in the vicinity so that data transmission runs smoothly. At a high quality surveillance camera So you can also run a very good cable. The cables come with me RJ-45 connectors at both ends and are ready for immediate use.

Anyone planning the complex wiring of an entire house should pay attention to the highest quality Installation cables grab - so you are future-proof. Because one thing is certain: the amount of data to be transferred will grow rather than shrink in the future. Where installation cables are not an option and there are still greater distances between the camera and router or network recorder, intermediate switches provide an inexpensive remedy - but these then require their own power supply.