This model was available for a long time in a variety of versions, with 4 pin or 3 pin, some have the switch on the attached stand bracket (the classic "Butterfield" one I believe) but the later ones had a switch on the main mic shaft (545S), there are also some 545L which have no switch and 3 pin connector on an attached cord that can be used as high impedence with an adapter. By the way, I have several of these laying around ( assorted types), if somebody is interested in buying one let me know offlist, this is another attempt to cut down on the clutter I've accumulated and they will be reasonable.
