[MetalFlame]

Eso-80 can be jammed.You cannot prevent the machine to take the measurment,but you can jam the radio connection between photo module and measuring device.In Germany people use PMR-radios(Alan-G7 are the easiest to modify) and they solder the bridge in the circuit in order to transmit on 434,7MHz(70cm-band)with greater power(around 1W).For sucessfull jamming you need around 0,5W transmitted power("snow").So,ESO-80 wil measure your speed,but the photo isn't taken.
Another(passive) way to detect it,is with scanner.That's not very realible,because the ESO-80 must be triggered in your scanning range in order to detect it.
There are 4 different ESO versions and only ESO80 uses radio connection.Other models use cable and those models are un-detectable.

Older Autovelox 104 also have radio connection and can be easily jammed.All you need to do is transmit around 1W of "snow"(white noise) on 26.6MHz. New Autovelox 105se and VeloMatic do not have radio connection and therefore cannot be jammed/detected.