Data Acquisition

Advantages of the system include:• Intelligent hubs are available that can determine which spurs from the hubreceive information. This improves on the security of the network – a featurethat has often been lacking in a broadcast, common media network such asEthernet.• Flood wiring can be installed in a new building, providing many more wiringpoints than are initially needed, but giving greater flexibility for futureexpansion. When this is done, patch panels – or punch down blocks – areoften installed for even greater flexibility.This standard, like the 10BaseT standard, is based on a star topology using wiring hubs.The actual standard had been delayed by development work in other areas, and wasratified in September 1993. It consists of three architectures. These are:• 10BaseFLThis is the fiber link segment standard that is basically a 2-km upgrade to theexisting fiber optic inter repeater link (FOIRL) standard. The original FOIRLas specified in the 802.3 standard was limited to a 1km fiber link between tworepeaters, with a maximum length of 2.5 km if there are 5 segments in thelink. Note that this is a link between two repeaters in a network, and cannothave any nodes connected to it.• 10BaseFPThis is a star topology network based on the use of a passive fiber optic starcoupler. Up to 33 ports are available per star, and each segment has amaximum length of 500 m. The passive hub is immune to external noise andis an excellent choice for noisy industrial environments.• 10BaseFBThis is the fiber backbone link segment in which data is transmittedsynchronously. It is designed only for connecting repeaters, and for repeatersto use this standard, they must include a built-in transceiver. This reduces thetime taken to transfer a frame across the repeater hub. The maximum linklength is 2 km, although up to 15 repeaters can be cascaded, giving greaterflexibility in network design.This is the preferred approach to 100 Mbps transmission that uses the existing EthernetMAC layer with various enhanced physical media dependent (PMD) layers to improvethe speed. These are described in the IEEE 802.3u and 802.3y standards as follows:IEEE 802.3u defines three different versions based on the physical media:• 100Base-TX which uses two pairs of category 5 UTP or STP• 100Base-T4 which uses four pairs of wires of category 3,4 or 5 UTP• 100Base-FX which uses multimode or single-mode fiber optic cableIEEE 802.3y:• 100Base-T2, which uses two pairs of wires of category 3,4 or 5 UTP.