For example: Agilent E4440A or Anritsu 68369
Counters/Timers
Racal Instruments R-2461-Cd
2461-Cd, 200MHz ,2-Ch UCT w/o Int.Frequency Std.
Manufacturer: Racal Instruments
Racal Instruments R-2461-Ce
2461-Ce, 200MHz,2-Ch UCT w/TCXO Int.Frequency Std.
Manufacturer: Racal Instruments
Racal Instruments R-2461-Cf
2461-Cf, 200MHz ,2-Ch UCT w/ OCXO Int.Frequency Std.
Manufacturer: Racal Instruments