For RR2000 used with a dummy amplifier on FDM track circuits, you’re essentially in the same voltage world as RR2280 / RR2300—just an earlier generation of kit.
Very tight summary:

• RR2000 dummy amplifier output (no load, FDM channel selected):
  ≈ 3–6 V AC
• This is the open‑circuit AF signal the set throws out.
• At the FDM receiver / track repeating relay input (with correct dummy load / links):
  ≈ 1–3 V AC
• Enough for a “track clear” condition and for the relay to pick and hold.
  If you’re seeing a couple of volts AC at the receiver input, that’s broadly right.
  

For an FDM Track Repeating Relay Receiver, the RR3000 with dummy amplifier is only meant to reproduce the small AF signal that would normally appear at the receiver input—not a big supply voltage.
In practice, you should expect roughly:

• Open‑circuit at dummy amp output:
  ≈ 3–6 V AC (depending on gain setting and channel)
• At the Track Repeating Relay Receiver input (with correct dummy load connected):
  ≈ 1–3 V AC for a healthy, “normal feed” condition
  So if you’re seeing a few volts AC at the receiver input (not tens of volts, and definitely not 24 V DC), you’re in the right ballpark.