Semi-adjustable articulator with mounted casts. An articulator is a mechanical device used in dentistry to which casts of the maxillary (upper) and mandibular (lower) teeth are fixed, reproducing recorded positions of the mandible in relation to the maxilla.
The Greek scholar Heron of Alexandria created the earliest known automatic door in the 1st century AD during the era of Roman Egypt. The first foot-sensor-activated automatic door was made in China during the reign of Emperor Yang of Sui (r. 604â618), who had one installed for his royal library.
Tum-tum' appears to have been originated in the 1890s, the linking of the tune to the rhythm of an actual knock comes later. The earliest example I have been able to find comes in: 1952 Peter de Vries No, But I Saw the Movie The door buzzer sounds seven times, to the rhythm of âShave and a haircut, two bits,â and the door opens.