Answer:
The prisoner's lack of control
Step-by-step explanation:
The bell symbolized the lack of control prisoners had over their own lives, as the author says, " It gave me orders and I executed them blindly" and "The bell regulated everything". These two sentences show that the bell is giving the person here edicts that the person is and has to follow. To Regulate means to 'control'.
How the person executes the orders blindly shows how they have no control.