The Model 1790 Tachometer Tester is used for testing and calibration of electrical and mechanical tachometer generators and indicators. A high-quality DC motor is coupled directly to a 1/4 inch square hole drive (AN Pad). This tachometer tester output can be converted to a wide variety of adapters and different tachometer interfaces. The motor drive control circuit uses SCR components and an open loop system for an economical solution to speed adjustment. The control panel consists of a five-digit LED display, momentary switches for start and stop, a direction switch, a display select switch, and a ten-turn potentiometer for speed adjustment.