The Type W is a differential comparator plug-in amplifier for 500-series scopes. Its bandwidth varies from 23MHz to 8MHz depending on gain. Only modestly faster than its predecessor, Type Z, Type W extends performance in terms of sensitivity, reaching 1mV/div. It achieves 20,000 to 1 common-mode rejection at DC and low frequencies. It has a built in precision variable voltage supply, "Vc", which is controlled by a ten-turn pot and can vary from either -1.1V to +1.1V or -11V to +11V. Type W has two signal inputs, "A" and "B". A mode switch selects between displaying A-Vc, A-B, or Vc-B. The "A-B" mode is particularly useful for displaying the current in a sense resistor, while the other modes provide "slideback" measurements of small variations superimposed on a large constant. An output of Vc is provided on the front panel of the Type W. Unlike Type Z, Type W has two gain axes, a decade attenuator and a 1-2-5-10-20-50 selector, reminiscent of Type D from ten years before. Type W is the only letter-series plugin with an "infinite resistance" input mode selectable at the front panel. (Type 1A5 has an internal jumper than can be cut.)
In the letter-series timeline of differential amps, Type W, introduced in 1965, follows Type Z and precedes Type 1A5. Types W and O were "in at the finish", available right up to the discontinuance of the entire classic plugin scope line in 1974.