Agilent Technologies 93000 SOC Series Training Manual page 103

Lesson 1 – Analog Modules
The following figure shows how to use one DUT pin for multiple
digitizers (high speed digitizer and high resolution digitizer) by
means of a loop back route:
Example of a Loop-back Route
In the above example, when K1 and K3 are closed and K2 is open,
the signal from the DUT can be measured by using the High Speed
Digitizer. In this case, the multiplexer of the High Speed Digitizer
establishes the input route to measure the single-ended signal.
When K1, K2, K4, K5 is closed and K3 is open, the signal from the
DUT can be measured by using the High Resolution Digitizer. In
this case, the multiplexers of the high speed digitizer and high
resolution digitizer establishes the loop back route and input
route, respectively.
The loop back routes are designed for high band width. The line
impedance is exactly 50 Ohm. Hence, by using the loop back route,
you can make a route that has better performance than using
additional user relays on the DUT board.
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