The old man had been using the radio to listen to the news at low volume and keep the ward informed of the goings-ons of the outside world. That night, though, the radio goes silent–not because the batteries run out, but because the announcer goes blind. Little by little, everyone goes to sleep satiated because, although the system under the man with the gun is brutal, it is efficient.
That night, the doctor's wife walks around the compound. First she goes outside and notices how disarmingly quiet everything is. Then she does some reconnaissance of the enemy ward. She finds that they have a guard who swings a stick back and forth across the corridor. Their ward is clean, with no one sleeping in the hall. She counts twenty men in the ward, including the man with the gun. She can also see that they have stockpiled food in containers by the far wall. On the way back she finds two blind people making love in the hall and is overwhelmed by compassion.
The old man's radio is another example of the decay of the modern world. Just like medicine, the economy and the government, communication is a system that is useless without people to run it. This means that it can reach a point where no one knows how or is able to run the operations necessary to, for example, make a radio broadcast. In this case, the system of communication might as well not exist.
We can see in this part the development of the foreshadowing of the wife's murder of the man with the gun. Just like the fact that she kept the scissors, though, the doctor's wife will not admit to herself that when she makes these reconnaissance missions she has a goal in mind. The doctor's wife is still not comfortable with what she will inevitably be called upon to do, that is, commit murder. It is precisely her attachment to who she is that differentiates her from the blind internees.
This is the second time that the doctor's wife has heard people making love in the quarantine. At first she was disgusted by their lack or propriety. Now, though, she sees that this form of connection may be all that these people have left. Their blindness has left them unable to connect on any more "elevated" level. Read allegorically, we can see that the loss of the faculty of reason–symbolized by their blindness–has left them not only unable to organize themselves or maintain any semblance of civilization but unable to love in any but the most base of ways. This connects, through the allegory, reason and love, showing that the first is a prerequisite for the latter.