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.
The following differential amplifier can be configured to display VA, −VB, VA−VB, VA−VC, or VC−VB.
This allows DC-coupled measurements of small signals with large DC offsets.
Unlike later comparators, Type Z has separate step attenuators 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.
With a pair of "Disconnect Signal" buttons, the Type Z was the first movement toward a "GND" position on the input switches.
Maximum sensitivity is 50 mV/div, and common-mode rejection at DC and low frequencies is 40,000 to 1.
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 uses both tubes and transistors, capitalizing on the strengths of each.
The step attenuators are turret attenuators.