up their audio gear to nominal reference level of 0 dB on a VU meter aligned to +4dBu or -20dBFs, in Europe equating to roughly +4 dBm or -18 dBFS. Peak signal levels must not exceed the nominal level by more than +10 dB. Broadcast audio as a rule must be as free as possible of Gaussian noise, that is to say, it must be as far from the noise floor, as is reasonably possible considering the storage or transmission medium. Broadcast audio must have a good signal-to-noise ratio, where speech or music is a bare minimum of 16db above the noise of the recording or transmission system. For audio that has a much poorer signal-to-noise ratio (like cockpit voice recorders), sonic enhancement is recommended. Non-standard video Although almost any video gear can create problems when broadcast, equipment aimed at consumers sometimes produces video signals which are not broadcast safe. Usually this is to reduce the cost of the gear, since a non-standard video signal in the home might not create the problems that one might find in a broadcast facility. Potential flaws exist with: VHS and 8 mm: Consumer devices generally lack time base correction that may cause problems with genlock and sync with some analogue and digital broadcast equipment. Consumer analogue video systems have greater system noise and lower chrominance and luminance than is normal for standard definition TV. As a general broadcast engineering rule all analogue videotape origin material should be genlocked before transmission, but this is not mandatory or necessary for all conditions. All analogue videotape by default is broadcast safe under normal playing conditions. Older videogame systems: Video game consoles before the sixth generation and 8-bit home computers generated a video signal lacking the half scan line needed to make interlace happen. This subtle simplification caused NTSC sets to scan 240p/60 instead of 480i60, with similar results for PAL. While this actually improved picture quality for the kind of low-definition images that videogames of this era generated, such a signal modification could cause problems in a broadcast environment as the signal behaviour is outside the original television system specifications. Genlocking—but not timebase correction—are the recommended broadcast engineering solutions. Computer video signals: Computer video can be set up to run at many different frame or field rates, ranging 50 frame/s to more than 240 frame/s. Computer video is generally progressive by default, but many interlaced modes