40VRMS Amp to ring old rotary phone

  I need to ring an old rotary phone. I have been looking over the net, and it looks like a 20Hz signal @ 40VRMS will do the trick. Is there something small I can build? I'm wondering if I can keep it within the phone housing. I know it's not super pro audio for this forum, but I don't know where else I can get great help like I've gotten here in the past with other pro audio stuff.

  Thanks as always,
 
  -P