YSI model 42SC UNTESTED This unit has a gage with three ranges, one from 70 to 150, one from 20 to 80 and one from -40 to 30.  A knob selects between the three ranges and also has an off position and an "adj. red line" position associated with an adjustment screw.  There are three connectors on the front, two labelled "recorder" and one labelled "probe". No probe is included. Thanks for looking