Real-world technology: airplanes, automobiles, diesel engines, phonograph records, radios, telephones, television and traffic signals.
Fictional technology: refractor rays (Gulch mirage), Rearden Metal, sonic death ray (Project X), voice activated door lock (Gulch power station), static electricity-powered motor, palm-activated door lock (Galt's NY lab), shale-oil drilling, portable X-Ray machine and nerve-induction torture machine
Traffic Signals
Early on, the book mentions the "screech" of a traffic signal as it changes. This implies the older technology of mechanical traffic signals, the kind which displayed a pennant or flag indicating stop or go, and the inverse indicator in the opposite direction. Traffic signals using lights have been around for over 40 years, so anything of this type is very old compared to today.
Rearden Metal
Rearden metal is a fictitious metal alloy invented by Hank Rearden. It is lighter than traditional steel but stronger, and is to steel what steel was to iron. It is described as greenish-blue. Among its ingredients are iron and copper.
Initially no one is willing to use Rearden metal because no one wants to stick his neck out and be the first to try it. Finally, Dagny Taggart places an order for Rearden Metal when she needs rails to rebuild the dying Rio Norte Line.
The first thing made from Rearden metal is a Bracelet.
Rearden metal is mentioned in sections 114, 121, 131, 148 and 161.