The semiconductor curve tracer displays a family of dynamic characteristic curves for transistors, FET's, diodes, Zener diodes, triacs, tunnel diodes and all other semiconductor devices on the screen of an oscilloscope. Most authorities agree that a dynamic curve tracer is the best instrument for testing semiconductors, since it simulates actual operating conditions of changing voltage and current. Some of the characterististics which may be measured are gain (beta), leakage, breakdown voltage, output admittance, linearity, effects of capacitance and effects of temperature. When first introduced, semiconductor curve tracers were primarily employed in engineering laboratories to select transistors with specific characteristics for design applications. Later the instruments became widely used for sorting, inspecting and testing semiconductors in production assembly and by technicians for troubleshooting. The latest application has been the discovery that curve tracers can be used for troubleshooting without removing the semi- conductor from the circuit. In addition, a semiconductor curve tracer offers several other servicing advantages. By matching characteristics, balanced and/or complementary pairs may be selected. Matching also allows sorting and selection of transistors for substitution, resulting in an inventory reduction of replacement parts. An oscilloscope must be used in conjunction with the curve tracer for the display. Almost any 3-inch or larger general purpose oscilloscope is satisfactory as long as it has external horizontal facilities, and is DC coupled. The B & K Models 1440, 1460 and 1465 Oscilloscopes are ideal companions for the Model 501A Curve Tracer. A graticule overlay for the oscilloscope screen and built-in calibration signals from the curve tracer makes the unit complete. The special 3-tip probe supplied with the unit simplifies in-circuit testing by contacting base, collector and emitter simultaneously with a single probe. This is very convenient for testing transistors mounted on circuit boards.