what you mean. If a detector has an ED of 120 phase it incorporates a certain level of discrimination at its lowest (minimum) discrimination setting whereas a detector with an ED 180, at it lowest discrimination setting, incorporates no discrimination.
In theory any detector in All Metal has no discrimination and therefore will signal on all ferrous objects (nails, small pieces of iron, etc.) irregardless of re-tune speed and whither or not it is motion based or non-motion based.
The graph illustrated indicates the lowest level (180 degree phase) that a detector in discrimination will yield an audio response. If the detector design limits it to a 120 degree phase it would eliminate/discriminate (again it theory) all objects below the 120 degree phase on the corresponding chart indicated by the left side of the chart.
Too further confuse the issue on some TID detectors the phase response, in discrimination, can be thought of to be a wheel (360 degrees) rather than a 180 degree phase and a -95 VDI response, which would in theory would be a ferrous object, could be a coin that because of the "wrap around" theory reads as a negative due to ground matrix, depth, etc.
The positive thing here is we don't require this determination on the Tesoro.
Pap