The Type Z Plug-In Unit is a calibrated differential comparator preamplifier designed for use in all Tektronix Type 530-, 540-, 550-, or 580-Series Oscilloscopes. The unit may be used for three different modes of operation: (1) as a conventional plug-in preamplifier, (2) as a differential input preamplifier, or (3) as a calibrated differential com-pa rator. As a conventional preamplifier, the Z Unit alone has a risetime of 24 nanoseconds and a maximum sensitivity of 0.05 volt per centimeter of deflection. Table 1-1 summarizes the risetimes and bandwidths available when the Z Unit is used in combination with various types of Tektronix oscilloscopes.