The CRB-S are giant robot dogs, quite a bit larger than their cyberdog cousins. Designed for non-lethal (in theory) containment of Denver's revolting population, three of these units were in use by the Denver City police department prior to the deployment of the National Guard.
One of Dog Town's quests is to get rid of these three robots, as they would continue to harass the player. An alternative is to reprogram one of them to follow the player as a companion (but only within Denver city limits) or to change the priorities of the robots and use them to drive out the dogs roaming the city, salvagers, Caesar's legionaries, etc.
It also had the Bonus Move perk, giving it 2 extra movement AP's. Other than the skills listed on the right, it also had Van Buren-specific skills, namely Programs = 50%, Electronics = 25%, Mechanics = 80%. Its starting XP score was 1111.
CRB-S is a reference to Cerberus, a dog who guards the gates of the Underworld, to prevent those who have crossed the river Styx from ever escaping.
The robotic dog companion concept was later reused for Fallout: New Vegas with Rex as they share background but in the finalized concept, he is a normal sized dog and is not stated to be deployed for a revolting population.