A ferroresonant transformer (also known as a Constant Voltage Transformer or CVT) made by the manufacturer FUBA was used in older CATV (Cable Television) systems as a robust and reliable power supply component. Its primary function was to provide a stable, regulated AC output voltage to power active components like line amplifiers in the cable network, even when the input AC mains voltage fluctuated significantly. Key characteristics and purpose in CATV systems:

  Voltage Regulation: It inherently provides a stable output voltage (typically within ±2-4%) despite input voltage variations of up to ±15-25% by using a magnetic core that operates in saturation. This was crucial in older CATV systems where power quality over long cable runs could be inconsistent.
  Power Conditioning: The design acts as a low-pass filter, effectively suppressing voltage transients, surges, and line noise, protecting sensitive electronics in the CATV equipment.
  Reliability and Durability: Ferroresonant transformers are known for their simple, robust construction (relying mainly on magnetics and a capacitor) with no complex electronic feedback loops, making them very reliable and durable in harsh outdoor or industrial environments.
  Inherent Short-Circuit Protection: The design naturally limits the output current during an overload or short circuit condition, preventing damage to the transformer and downstream equipment.
  Isolation: Like any transformer, it provides electrical isolation between the primary (input) and secondary (output) circuits, which is important for safety and noise reduction. 

FUBA (Fuba Communications, a German company, now part of the Blankom group) was a known supplier of professional equipment for cable and satellite reception technology, including power supplies that utilized this ferroresonant technology. This technology has largely been replaced in modern systems by more efficient switching power supplies, though at the time, ferroresonant units offered excellent performance for the specific needs of a CATV network