looks like there are only the scales and the RJ11-connector,
but the following info may be helpful from the http://www.maplin.co.uk/p/maplin-replacement-anemometer-for-n25fr-n76nf
· 10 months ago
Internally, it is just a reed switch that is closed by a magnet on the rotating head. This means that there is one brief switch closure for every complete revolution of the head. The 2-wires to the RJ-11 connector (positions 3&4) come from the two terminals of the reed switch.