Provided are techniques and apparatuses for determining the geographic location of a node on a network. An example method includes sending a signal to a first hearing prosthesis and a second hearing prosthesis. Such devices may include iron sights of small arms weapons, and cameras and telescopes, which may be either electrically or manually focused. The compounds of the invention comprise a ring coupled to a heterocyclic nucleobase that lacks an \u201cO2 carbonyl\u201d, that enables them to selectively react with and inhibit viral reverse transcriptase, while remaining substantially unreactive toward human DNA polymerases. The anvil lugs are coupled to the ring gear and are not engaged by the planet gears. ; R3 is \u2014CH2\u2014CH2\u2014CH2\u2014CH2\u2014CH\u2550CH\u2014COOR4, \u2014CH2\u2014CH2\u2014CH2\u2014CH2\u2014X1\u2014CH2\u2014COOR4, \u2014CH2\u2014CH\u2550CH\u2014CH2\u2014X1\u2014CH2\u2014COOR4 or \u2014CH2\u2014CH2\u2014CH2\u2014COOR4; R4 is hydrogen, etc.