The engineer may mix programming that will sound pleasing on the widest range of playback systems used by regular listeners (i.e. high-end audio, low-quality radios in clock radios and "boom boxes", in club PA systems, in a car stereo or a home stereo). While some broadcasters like the BBC generally believe in using monitors of "the highest practicable standard of performance", some audio engineers argue that monitoring should be carried out with loudspeakers of mediocre technical quality to be representative of the regular systems end-users are likely to be listening with; or that some technical defects are apparent only with high-grade reproducing equipment and therefore can be ignored. However, as a public broadcaster dealing with a lot of live material, the BBC holds the view that studio monitors should be "as free as possible from avoidable defects". It is argued that real life low-grade sound systems are so different that it would be impossible to compensate for the characteristics of every type of system available; technical faults must not be apparent to even a minority of listeners while remaining undetected by the operating staff. It is further argued that, because of technical progress in the science of sound transmission, equipment in the studio originating the programme should have a higher standard of performance than the equipment employed in reproducing it, since the former has a longer life.