time t3 at time t4 the sustain waveform is returned to the 100 volt level by first biasing 34 off 34 fet 45 then biasing 34 on 34 fet 50 to discharge the line 95 to the voltage across capacitor 90 100 volts through diode 70 capacitor 90 and fet 50 the process is repeated at time t5 by biasing fet 55 34 off 34 and fet 60 34 on 34 to produce the initial conditions as at time t1 it may also be observed that the single sided sustainer circuit of fig2 may be operated in a manner to provide a 200 volt peak to peak square wave without the return to 100 volt midpoint feature this is accomplished by operating fet 55 at the same time as fet 45 such that both fet 39 s 45 and 55 are biased 34 on 34 whenever fet 39 s 50 and 60 are biased 34 off 34 and vice versa initially with fet 39 s 50 and 60 biased 34 on 34 and 45 and 55 biased 34 off 34 the horizontal line 95 will be pulled through the horizontal driver module to ground and capacitor 90 will be charged to the source voltage as described above as fet 39 s 50 and 60 are biased 34 off 34 and 45 and 55 are biased 34 on 34 the voltage 2v s is applied to line 95 through fet 39 s 45 and 55 and capacitor 90 which was previously charged to 100 volts by repeating this process a zero to 200 volt square wave is generated at line 95 diodes 70 and.