The X-30 and 305 will appear to "lock on" to a single TID number better than the X-50 or 505. And all 4 of them appear to "lock on" to a single TID number better than the X-70 or 705. Reason being is, the fewer the notch segments, the wider the notch. More notch segments = more narrow notches and allow for more TID number options.
For example, if you dug a target with the X-70 or 705 that read a 36, it would also read a 36 on the X-30, 305, X-50 and 505 because they all have a notch number 36 available in their software.
Not to complicate matters, but if a target bounces between say a 36 and 38 on the X-70 or 705, it will lock on to a TID of 36 on the X-30, 305, X-50 and 505 because they don't have the capability of displaying a number 38. In actuality, that target may be trying to tell us it's conductive value is really a 37, which none of them have. The reason it bounced between 36 and 38 on the X-70 and 705 is because 37 is smack dab in the middle. On the X-30, 305, X-50 and 505, a 37 is closer to 36 than either the next highest number (40) on the X-30 and 305, or (39) on the X-50 or 505. So that specific target (pretend value of 37) will likely "lock on" a 36 for the X-30, 305, X-50 and 505, but "bounce" between 36 and 38 on the X-70 and 705. JMHO HH Randy