Where it is Boost.Signal?

I kept reading about a library named Boost.Signal. I think that this library is about signal and slots. But I can't find it in Boost. Can someone tell me where it is, please? I look for it in the Files section and in the CVS repository but i can't find it. Thanks in advance. -- Raúl Huertas Díaz rhuertas at tcpsi dot es http://www.tcpsi.es