HP 54710A User's Reference Manual page 231

Measurements
Time-interval measurements
Other factors that influence accuracy
The HP 54720 can be operated in either real-time or equivalent-time
sampling modes. The following discusses the advantages and disadvantages
of each mode.
Real-Time Sampling
In real-time sampling, all the samples are acquired and digitized on every
trigger as shown in figure 13-21. There is a simple, direct correspondence
between the samples and the time that they were acquired. Single-shot
measurements require real-time sampling.
Figure 13–21
Sampling Techniques
13–46