For example: Agilent E4440A or Anritsu 68369
Racal Instruments
Racal Instruments R-11-9191
Ce,Spare 200MHz,UCT (TCXO Freq.Std.) Plug-In Card
Category: Plug In / Part / Component / Module
Racal Instruments R-11-9193
Cf,Spare 200MHz,UCT (OCXO Freq.Std.) Plug-In Card
Category: Plug In / Part / Component / Module
Racal Instruments R-2461-Cd
2461-Cd, 200MHz ,2-Ch UCT w/o Int.Frequency Std.
Category: Counters/Timers
Racal Instruments R-2461-Ce
2461-Ce, 200MHz,2-Ch UCT w/TCXO Int.Frequency Std.
Category: Counters/Timers