For example: Agilent E4440A or Anritsu 68369
Elgar AC Power Supplies
Programmable AC Power Sources, Frequency Converters
Elgar CW1251P
CW1251P 1250 VA, ContinuousWave Power Source - Programmable - CW Series
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Manufacturer: Elgar
Elgar CW2501M
AC Power Source, 2.5 KVA, 1Ø, 135/270 VAC, 45 - 500 Hz (1 KHz optional)
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Manufacturer: Elgar