# What do you mean by 'active switch' in the manual?
-The only active switch we're aware of is the Featherweight Magnetic Switch
-sold by [Featherweight Altimeters](https://www.featherweightaltimeters.com)
+The only active switch we're aware of is the
+[Featherweight Magnetic Switch](https://www.featherweightaltimeters.com/store/p4/Magnetic_Switch.html)
These need three connections .. a ground, an input, and an output. Of
the two switch screw terminals on Altus Metrum products, one is