and maximum level 0. Thus sound recordists using location mixers would typically send a tone at 0 VU or PPM 4 (British) and adjust the Nagra recorder's gain to read −8 on the modulometer. Some newer digital recorders, e.g., the Nagra VI, have modulometers displayed as bargraphs calibrated in dBFS. For these, Alignment Level is as for any other digital PPM, i.e., −18 dBFS (EBU) or −20 dBFS (SMPTE). Usage of meter by sound balancers To use PPMs effectively to control sound levels it is necessary to understand design rationale and limitations. Many engineers prefer the PPM to the much slower VU meter used in the US—but it does require some interpretation in use. Though it gives a useful overload warning, it does not represent either true peak level or subjective loudness. The BBC have tables showing recommended settings for different types of programme, such as speech, classical music etc., which attempt to take account of the latter. Regardless of the kind of programme, there is usually a nominal Permitted Maximum Level, as indicated on a PPM. Operators are expected to keep levels below it, within reason. Practices vary between countries and organisations. In the UK, the Permitted Maximum Level is 8 dB above Alignment Level, corresponding to '6' on the British PPM scale. ITU-T standards for international sound programme circuits specify a Permitted Maximum Level of 9 dB above Alignment Level. Accordingly, +9 dB is represented by a mark on the EBU PPM scale. Digital audio levels Because quasi-peak PPMs indicate neither loudness nor true peaks but something between the two, it is important to allow sufficient headroom when using them in the control of digital audio levels. The EBU convention (R68) provides for this by defining Alignment Level as −18 dBFS. Thus a peak to the Permitted Maximum Level as indicated on a quasi-PPM corresponds to −9 or −10 dBFS. This 9-10 dB margin allows for operator error, the true peak typically being several dB higher than the PPM indication, and that subsequent signal processing (e.g., sample rate conversion) may increase the amplitude. SMPTE RP 0155 recommends a different alignment level, corresponding to 0 VU, of −20 dBFS. The two conventions result in line-up tone levels that differ by 2 dB, but in practice the level of programme modulation tends to be similar. The SMPTE and the EBU agree that regardless of whether −18 or −20 dBFS is