Operation 
Frequency Measurement
 with 
External Reference
 (Option
 1E) 
1.
 Connect a precision frequency standard signal (must have an accuracy better 
than 10 ppm) to BNC connector EXT REF IN, located on rear panel. The 
reference signal must be greater than 2 V peak-to-peak into a 50
 Q
 or 75
 Q 
load with frequency of
 1
 MHz, 3.579545 MHz, 4.4336188 MHz, 5 MHz, or 
10 MHz. 
2.
 Select FREQUENCY as described above. 
3. After 100 measurements (approximately
 1
 minute), the frequency readout will 
display the applied input signal frequency in 8 digits. 
Delay Sweeps by Event
 Counts 
The Counter/Timer/Trigger (Option 09 or 06) includes delay-by-events for either the 
A Sweep or the B Sweep. Event counting begins at a starting event on a vertical 
input, defined by the A Trigger. Delay-counting events are defined by the B Trigger. In 
addition,
 the available Word Recognizer
 (WR) can
 define either start or delay-counting 
events. The combinations available are shown in Table 2-3. 
Which
 Sweep to
 Delay 
When the A Sweep is delayed by events, the event count can accumulate 
for unlimited time. Then the B Sweep can be delayed by time to magnify 
waveform details. 
When the B Sweep is delayed by events, the event count must accumulate 
during the A Sweep. Then the intensified A Sweep can show the timing 
between the start event and the delay count. 
2-28  2465B/2455B/2445B Operators