Position and draft control system for plows

In a control system for a plow including frame means arranged to extend angularly from a forward end to a rearward end, a plurality of plow bottoms carried by said frame means, first wheel means for supporting a first portion of said frame means and second wheel means for supporting a second portion of said frame means spaced rearwardly from said first portion, power source means, and first and second electrically controllable level control means supplied with power from said power source means for effecting changes in the elevation of said first and second portions of said frame means with respect to said first and second wheel means, first and second level control circuits electrically coupled to said first and second level control means, each of said circuits having first and second inputs and being operative to apply signals to the corresponding level control means to raise and lower the corresponding portion of said frame means in accordance with the difference between signals applied to said first and second inputs, first and second adjustable means coupled to said first inputs to apply signals of adjustable magnitude thereto, first and second position sensing means mechanically coupled to said control means and electrically coupled to said second inputs to apply signals to said second inputs corresponding to the levels of said first and second portions of said frame means, and control circuit means for preventing operation of one of said level control means at any time when the other of said level means is operative in performing either a raising or a lowering operation to thereby prevent simultaneous operation on both of said level control means and to thereby minimize the load on said power source means.