Bad books do not bind circuits

In the bad book unbinding circuit shown in the figure above, YV1 is the execution solenoid valve that controls the machine head to unbind bad books. Under normal circumstances without a bad book signal, the left tube VTI of the bistable trigger is cut off, and the right tube VT2 is turned on, and the collector voltage of VT2 is ov at this time. If a bad book signal enters the flip-flop, the flip-flop flips, and its state is that the left tube VT1 is turned on, the right tube VT2 is turned off, and the collector voltage of vri is +9 .5V. This signal is amplified by current VI'3, and controls VT4 to conduct, causing relay Kl to close, and electromagnetic valve YV1 to act, controlling the machine head not to bind bad books.