  Transverse feedback systems for controlling the vertical coupled-bunch
instabilities in the positron and electron main rings are installed at DAFNE.
They started to be operative respectively from June and September 2000. For the
horizontal plane, similar systems have been installed in summer 2001 with less
kicker power. Design specifications and the basic system concepts are
presented. Real time bunch-by-bunch offset correction is implemented using
digital signal processors and dual-port RAM's. Fast analog to digital sampling
is performed at the maximum bunch frequency (368 MHz). The system manages at
full speed a continuous flow of 8-bits data and it has the capability to invert
the sign or put to zero the output for any combination of bunches. A conversion
from digital to analog produces the output correcting signal.
