Now, on the maps the bright green areas shown where the signal from this transmitter is strong, dark green areas are poorer signals. Those parts shown in yellow may have interference on the same frequency from other masts.
The next change is that the frequency usage maps (such as C21 (474.0MHz) after switchover) show the polarity (the position the receiver aerial has to be in) by the use of a black triangle to show "vertical".
barry swain : Hi, Barry. I'm afraid we can't tell you the reason for your not being able to update your box unless you can tell us the make and model of your box and preferably the date you purchased it - the nearest year would probably do for that. Reply back with this information and then one of us should be able to help you. Richard, Norwich.