text: Regen units were used in old pulse dial systems to clean up the pulse waveform on long distance calls.\n\nThe old rotary dials generated a number of pulses (on/off) = to the number dialed. \nOver a long line, or if routed through trunk exchanges the signal is attenuated so you can't tell on from off.\n\nA regen unit redials the number afresh before the signal is lost.\n\nthey were fun to maintain, lots of pins flying everywhere like a gattling gun.\n\nIn a modern system this will be a dull box that takes a signal in and cleans it up digitally.