High Speed Digitizers
A high speed digitizer has a variety of modern names such as low profile digitizer, low profile oscilloscope, PXI, AXI or multichannel data acquisition system; all are different terms for acquisition systems based on alternative (typically compact) form factors.
They are comprised of capturing electrical waveforms similar to an oscilloscope via an Analog-to-Digital Converter (ADC), stored in fast DDR memory, processed by a localized measurement system or user interface on a CPU or FGPAs for final analysis. Common applications using high speed digitizers are:

Tektronix LPD64 8 GHz Low Profile Digitizer
Frequency Range: 8 GHz
25 GS/s on all 4 Channels
With the lowest input noise and up to 8 GHz analog bandwidth, the 6 Series Low Profile Digitizer LPD64 provides the best signal fidelity for analyzing and debugging signals in a compact 2U rack space.

Tektronix MSO58LP 1 GHz Low Profile Oscilloscope
Frequency Range: 1 GHz
8 Analog Channels, 64 Digital Channels (OPT)
In applications that demand extreme channel density, the 5 Series MSO58LP Low Profile oscilloscope sets a new standard for performance.