For example: Agilent E4440A or Anritsu 68369
Keysight / Agilent Counters
Keysight / Agilent 08591-60073
HP Agilent Keysight 08591-60073 Counter Clock Board Assembly
Manufacturer: Keysight / Agilent
Keysight / Agilent 53151A
Agilent 53151A CW Microwave Frequency Counter, 26.5 GHz
Manufacturer: Keysight / Agilent
Keysight / Agilent 53200U-106
Add 6 GHz CW Microwave Channel UPGRADE
Manufacturer: Keysight / Agilent
Keysight / Agilent 53200U-115
Add 15 GHz CW Microwave Channel UPGRADE
Manufacturer: Keysight / Agilent
Keysight / Agilent 53210A
RF Frequency Counter, 350 MHz, 10 digit/sec
Manufacturer: Keysight / Agilent
Keysight / Agilent 53220A
Universal Frequency Counter/Timer, 350 MHz, 12 digit/sec, 100 ps
Manufacturer: Keysight / Agilent
Keysight / Agilent 53230A
Universal Frequency Counter/Timer, 350 MHz, 12 digit/sec, 20 ps
Manufacturer: Keysight / Agilent