For example: Agilent E4440A or Anritsu 68369
Counters/Timers
BK Precision 1823A
2.4GHz Universal Frequency Counter with Ratio Function
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Manufacturer: BK Precision
BK Precision 1856D
3.5 GHz Multifunction Counter (Frequency, Period, Totalize)
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Manufacturer: BK Precision
Racal Instruments 407494-011
2251A, 200 MHz Univ. Ctr./Tmr. w/Int. Precision
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Manufacturer: Racal Instruments
Keysight / Agilent 5223L
FREQUENCY COUNTER TO 300 KHZ WITH PERIOD AVERAGE AND RATIO
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Manufacturer: Keysight / Agilent
Keysight / Agilent 5300B
Measuring System Mainframe with Universal Counter
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Manufacturer: Keysight / Agilent