English: Vintage Grebe MU-1 Synchrophase AM radio receiver with gold-plated escutcheons, battery operation, circa 1925. This is a 5 tube tuned radio frequency receiver having two tuned radio frequency stages, a grid-leak detector stage, and two stages of audio amplification. The 3 tuned circuits must be tuned simultaneously in tandem in order to keep the radio operating when tuning in a new station, so the 3 tuning knobs are in the form of thumbwheels which can each be adjusted by a finger, so 3 hands are not needed.