The Tektronix Type Z is a comparator plug-in for 500-series scopes. Its two main subsystems are a differential amplifier and a precision variable DC voltage source, which can be used as one of the amplifier inputs. This allows DC-coupled measurements of small signals with large DC offsets. Its maximum sensitivity is 50 mV/div, and it achieves 40,000 to 1 common-mode rejection at DC and low frequencies. Its risetime as a general-purpose amplifier is 27 ns (13 MHz bandwidth), but it can track a common-mode risetime of 7 ns.
The Type Z has two inputs, A and B, plus a precision comparison voltage, VC, that is adjustable from 0 to +/-1 V, 10 V, or 100 V via a ten-turn pot. It's possible to view VA, -VB, VA-VB, VA-VC, or VC-VB.
Unlike later comparators, it has a separate step attenuator for each input, permitting the user to view the difference between signals of widely differing amplitudes. It is also the only comparator that can handle +/- 100 V common mode at full sensitivity. The Type Z uses two turret attenuators.
With a pair of "Disconnect Signal" buttons, the Type Z was the first of the movement toward a "GND" position on the input switches.
The Type Z was introduced in 1960 and uses both tubes and transistors, capitalizing on the strengths of each. It was dropped after 1968.