The driver circuit is basically an emitter-follower circuit tuned to produce ten volts at the emitter. The output from the voltage comparator is connected to the base of the transistor. When the comparator output is open, current will pass into the base of the transistor causing current to flow from the emitter. When the comparator output is grounded, the base of the transistor is also grounded. No current will flow through the emitter. Here is a simulation of the comparator switching the driver circuit.consumption very economic.