A tester is an electronics device that is well arranged and packaged in a good looking plastic casing
The cable tester is used in testing either signals, voltages,connections and continuity of a connection in various fields.The basic components of a typical cable tester include battery, connection point, indicator lights, leads may be black and red in colour, while some comes with indicator alarms to dictate or send signal of either wrong or right depending on its calibration terms.
basically in networking field an optical cable tester is use to test the different categories of ethernet cables such like CAT5, CAT6 and CAT5e.
and be sure that the Ethernet cables are firmly clipped to the connectors and that they make proper contact with connectors for effective transmission over a network.
they are used to verify if the cable connection is either straight through or crossover before being used in any equipment.
This peces of equipment is also used in an advanced way to verify signal loss of optical cables and connections.
The cable tester has an indicating light visible to eye which shows that the cables are either connected or disconnected in other-words if the eight lights are showing like in most cases red lights,
it means that the cable is probably and firmly clipped, hence it will also indicate that you made either a cross over cable or a straight through cable, but if some light are missing in between that shows an error and calls for immediate amendment.