Tech Fact

In cabling terms it is possible for the energy that is used to carry a signal travelling along one piece of cable to affect another nearby cable. This electromagnetic interference can have the side effect of causing parts of a signal being carried along one cable to cross over onto the other cable. This is known as crosstalk and can result in unintended signal disruptions. This is particularly a problem for cables that run in parallel as the amount of interference builds as the distance increases.

In networking cables that require high-speed reliable performance, crosstalk can be reduced by using twisted pairs of cables. The twists in the cables help reduce the amount of crosstalk between the cables as the electronicmagnetic interference, which is likely to be similar in a pair of twists, gets reflected back effectively cancelling out much of the interference.

A common network cable is UTP (Unshielded Twisted Pair) and others include additional noise reduction methods such as STP (Shielded Twisted Pair) and the addition of a thin foil outer layer to make FTP (Foil Twisted Pair) and SFTP (Shielded Foil Twisted Pair).

This definition is bought to you by: Jason Slater Weblog Tech Fact.

Fibre installations often consist of multiple cores (for example ours is eight core) but often few of these cores are used (we only use two). The others are only used in case of failure - or to handle increases in network demands. This unused fibre (also known as Unlit fibre) is referred to as Dark Fibre - an indication that fibre requires light to operate.

Fibre is typically used for infrastructure installations (although more recently for desktop installations too) and difficulties and high costs may be encountered physically laying the optical fibre as it needs to be handled with care (the cores are very delicate). This fibre may also be installed underground or in other difficult to access places. Because of this it is common to put extra fibre in at the time of installation to reduce costs in running extra lengths at a later date.

This definition has been bought to you by: Jason Slater Weblog Tech Fact.

The traditional method of receiving electronic mail (e-mail) used pull technology (such as POP). In this scenario you configure your e-mail to periodically connect to your e-mail provider and retrieve any message.

In a mobile environment where data rates are still chargeable this can be problematic as polling every fifteen minutes (or more frequently) can quickly build up your data charges.

In a push e-mail environment an initial connection is made from your client to the e-mail server and the connection between the two is kept open for periods of time. Some systems use a regular pulse-signal (also called a ping and a heartbeat) to tell the connection to stay alive (this is a much smaller overhead than performing a full poll).

I was surprised recently to hear someone tell me that Blackberry is the only push e-mail provider - maybe this was true a long time ago but these days Microsoft ActiveSync is a competitive push e-mail technology.

This definition has been bought to you by: Jason Slater Weblog Tech Fact.