The apparatus 1, further comprising a switching element operable to selectively connect {TAIL ~ the surface region} to {HEAD ~ a source} of potential that is at a reset level 
The apparatus 1 , further comprising a switching element operable to selectively connect { TAIL ~ the surface region } to { HEAD ~ a source } of potential that is at a reset level
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH