The IBM 3705 was the oldest of the family. The IBM 3725 was a large-scale node and front end processor, and the IBM 3720 was a remote node that functioned as a concentrator and router. IBM does not support 3705, 3720, 3725 starting from 1999.
These machines are followed by the IBM 3745, which provides up to eight T1 circuits. It is no longer marketed, but still supported and used.