The BBC now uses M6 in both radio and TV, although much legacy equipment is still configured for the 'traditional' M3 standard. European Broadcasting Union The EBU PPM is a variant of the British PPM designed for the control of programme levels in international programme exchange. It is formalised as the Type IIb PPM in IEC 60268-10. It is identical to the British PPM except for the scale plate, which is calibrated in dB relative to Alignment Level, which is marked 'TEST'. There are also ticks at 2 dB intervals and at +9 dB, corresponding to Permitted Maximum Level. United States In the late 1930s PPMs were considered for use in the US, but rejected in favour of a 'Standard Volume Indicator' (VU meter) on grounds of cost. Joint research by CBS, NBC and Bell Labs found that using an experimental design of PPM (with a relatively long integration time of 25 ms) in the control of programme levels gave only a 1 dB advantage over the VU meter, in terms of average output level for a given amount of distortion. It was felt that this was too small to justify the much greater expense. It was also found that VU meters gave more consistent readings than PPMs when comparing programme levels at the sending and receiving end of long lines subject to group delay, which altered the waveform. This finding has been disputed by others. A widely believed myth is that the PPM was developed as a superior alternative to the VU meter. In fact, the PPM came first, and if anything the VU meter was developed as an economical alternative to the PPM. By 1980, ABC had about 100 PPMs in use in control rooms in New York and its Washington News Bureau, and was ordering new consoles with PPMs fitted. These were Type II PPMs with the seven marks labelled −22, −16, −12, −8, −4, 0 and +4. ABC found that a modified version of the EBU meter based on the VU-meter 'A scale' was best, since it let operators use their usual jargon such as 'zero level' etc. The appearance is similar to an EBU scale except that the numbers are 8 dB lower. To aid alignment on both VU meters and PPMS, ABC in New York used a special test signal known as ATS. A 440 Hz tone alternated between steady tone at +8 dBu