Danbury is being called Connecticut’s top “signal city” — a place where economic trouble shows up before it spreads statewide. A survey of more than 3,000 business leaders found Danbury often feels job losses, housing shifts and consumer slowdowns first. The study by MarketBeat says Danbury’s location near New York and its mix of warehouses, service jobs and retail make it a sharp indicator of middle-class confidence. New London and Waterbury were also named key signal cities.