Voice, video and data are conveyed in a variety of different ways and those engaged in these fields will need a suitable tool kit and an appropriate level of expertise. Specialised equipment will also be required, both for installation work and for troubleshooting and repair. Many of the most frequently encountered problems arise not from equipment failures but in network cabling, and many pieces of kit have been developed to make the location of these faults much simpler. This, of course, requires much more than a multimeter or continuity tester, and many advanced LAN measurement devices are able to both monitor the performance of each element of a network and physically locate the position of any problems. Fibre optic-based systems require their own technology and problems often have to be located visually, often employing a fibre optic source or specialist video microscope. The telephone line tests may involve tone and probe equipment, and the testing of interfaces, such as RS232, may necessitate the use of breakout box types of testers to check the functioning of each pin. Instruments are available for all of these uses plus many more.