How is the mechanical hound used as a propaganda device in Fahrenheit 451?

The news media endlessly shows off the Hound's hunt so that people are so frightened of the Mechanical Hound that they will be deterred from lawbreaking.

The main law everyone seems concerned about is owning and reading books.  This is illegal, and if a citizen breaks this law firemen will burn that citizen's house and the books in it.  People who try to run away or do not surrender are chased down and captured by the Mechanical Hound.  The news media praises the Hound, making everyone aware of its capabilities.

Montag is frightened of the Mechanical Hound, even though as a fireman he is supposedly on its side.

The Mechanical Hound slept but did not sleep… Light flickered on bits of ruby glass and on sensitive capillary hairs in the nylon-brushed nostrils of the creature that quivered gently, gently, gently, its eight legs spidered under it on rubberpadded paws. (Part I) 

Montag has always felt uneasy about the Hound.  It seems alive and not alive at the same time.  It has a special stinger where it can drug its prey so that he or she can be captured.  Montag also feels the Hound has been treating him differently, perhaps even suspecting him.  He thinks he hears it sniffing at his house. 

Montag comes in one day and the Hound is not in its kennel.  He gets nervous, especially since Beatty is acting strangely.  He is quoting a lot of authors no one is supposed to be allowed to read.  The Mechanical Hound is not the only one who is suspicious, and its absence means Beatty is on to him. 

When Mildred turns Montag in, he is afraid to run because of the Hound.  He thinks the Hound will capture him before he can escape.  He is speaking to Faber in a special earpiece.  Faber asks him if he can run, and he says he can’t because of the Hound.  Beatty thinks he is talking to him and taunts him with threats of the Hound.  Montag kills Beatty and runs.  The Mechanical Hound that was chasing him is destroyed in the fire, but when Montag is on the run the media gleefully predicts he will never be able to get away from the Hound: 

"Mechanical Hound never fails. Never since its first use in tracking quarry has this incredible invention made a mistake. Tonight, this network is proud to have the opportunity to follow the Hound by camera helicopter as it starts on its way to the target" (Part III) 

The media relentlessly tracks and praises the Hound as the Hound tracks Montag.  If citizens ever consider hiding a book, coverage of the Mechanical Hound might dissuade them from doing so. 

Despite its ability, the Hound does not catch Montag.  He and Faber distract the Hound, and another unfortunate soul is caught instead.  The Hound must have its prey, and the cameras must have their victory.