The signal chain in sampling oscilloscopes contains a sampler, which measures the input signal at a moment in time.
Another setup is to have the sampler in a sampling head, e.g., the S-4. Sampling heads sometimes plug directly into the oscilloscope mainframe, e.g., in the 11801. In other cases, the sampling head plugs into a vertical plug-in, e.g., the 7S11, which plugs into the oscilloscope mainframe. Sampling heads can also be used on extension cables, e.g., the 012-0125-00, which allows the path between the device under test and the sampling head to be as short as possible for minimum signal degradation.
Tektronix sampling oscilloscopes use at least four different circuits: one-diode, two-diode, four-diode, and six-diode.
This is used in the Type N.
Tek S-1 sampler
Tek 3S76 sampler