M-J, from what I remember seeing at Scottish & West Drayton, as soon as someone presses the transmit switch on 121.5 the whole board lights up with red, intersecting lines - number dependent on various things, mainly reception, and the more the better as a more accurate fix can be obtained. There must be someone lurking here who is either a current or former D&D member of staff who can explain it better than I. It's quite impressive to see. Having said that, it took three calls before I was heard by them but it was an equipment failure NOT their fault.