Faber invented a device that looks like a seashell radio but is actually a two-way radio.
People use little seashells to listen to the radio. When Montag finally convinces Faber that he wants to be part of the underground movement to save the books, Faber gives him a special radio that looks like a seashell but is actually his own special invention.
"Go to the firehouse when it's time. I'll be with you. Let's listen to this Captain Beatty together. He could be one of us. God knows. I'll give you things to say. We'll give him a good show. …” (Part 2)
Faber describes himself as a coward, sitting at home as the Queen Bee while he sends out his worker drones to spy for him and get him information. He sends Montag to the fire house to get information. With Faber in his head, Montag feels better about navigating the land mine of treachery he has gotten himself into.
The old retired professor, Faber, has invented a device that is similar to a walkie-talkie, only it is a mere ear-piece. With this device, he can transmit messages and the receiver of these messages can hear him. In this way, Faber protects himself and others who treasure the value of works of history and of literature. When Faber talks to Montag, he "held his hand over his left coat pocket and spoke...words gently...."
As he begins to trust Montag when he first telephones, Faber leads the fireman into a small room where there is a table with numerous metal tools and a "welter of microscopic wire hairs, tiny coils, bobbins and crystals" lie. Montag asks the old professor what all these things are. "Proof of my terrible cowardice," Faber replies. He adds that electronics and radio transmission have been hobbies of his, and in his cowardice he has been forced to design a device that he shows Montag.
He picked up a small green metal object no larger than a .22 bullet.
Further, he tells Montag that after Montag first talked to him long ago, he has hoped the young man would return. Montag observes, "It looks like a Seashell Radio."
The transmitter is shaped like a small green bullet so as not to draw attention or suspicion from authorities. With this device Faber stays in touch with those who still love literature and the written word. After he gives Montag one of these devices, Faber stays in touch with the fireman and advises him what to do. This device eventually saves Montag's life as he has Faber to direct him to the place where he will be safe with other lovers of books.