The 577-177-D1 (Storage) or D2 {Non-Storage) Curve Tracer system is a dynamic component tester that permits display of characteristic curves of many types of devices, including: bipolar transistors, field effect transistors, silicon-controlled rectifiers, uni-junction transistors, MOS- FETS, integrated circuits, light coupled devices, capacitors, and relays. The D1 Display Unit features Split-screen storage, 6 1 /2-inch CRT, variable stored brightness, and a beam finder. The D2 Display Unit features a 6 1 /2-inch CRT and a beam finder. The features of the 577 Curve Tracer are: A collector supply variable from 0 to 1600 volts in several operating modes, including AC. The current available varies from 10 A {20 A Pulsed) on the lowest voltage range to 40 mA (80 mA Pulsed) on the highest voltage range. The collector supply power is set using a switch that changes series resistance to maintain the same peak power setting as the voltage range is changed. The collector supply is automatically disabled when the vertical display exceeds 2.5 screen dimensions, helping to protect the device under test from destructive currents. Switching the collector supply polarity automatically changes the polarity of tile step generator and re-positions the display start to the appropriate position on the CRT screen.