Norm, before I decided that optical sensors were easier and was still using reed switches I discovered that the magnet did not need to pass by the glass envelope with the reeds but that the leads were steel and a magnet passing by a lead could close the reeds. I am not sure if this is the case on all reed switches but it was on all I ever bought. I did all sorts of shaping of the leads to adjust the timing of the closure of the reeds from bending them into a U to twisting them into a spiral or even an L shape . These configurations allow for a very sharp rise and fall of the magnetic field. One configuration I liked was the L where the magnets circular path was tangent to one leg of the L and you cut the length of the leg to adjust the duration of the closure. The reed switches can even be anthwartship between two wheels on an axle with magnets passing by both leads. j
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