In debugging of WAN, the router at one side uses E1/CE1, and the counterpart at the other side uses serial port, so how to realize the intercommunication between both?
Both E1/CE1 and V.35/V.24 are at physical layer, and they are transparent to link layer, so they could interact through upper layer protocols if only the physical connection is well. Generally, V.35/E1 protocol converter is used to connect V.35 and E1/CE1 cables, and V.24/E1 protocol converter to connect V.24 and E1/CE1 cables.
Topology: Router (serial port)--V.35 cable--V.35/E1 protocol converter--E1 line--Transmission--E1 line--(E1/CE1 interface) Router;
alternatively: Router (serial port)--V.24 cable--V.24/E1 protocol converter--E1 line--Transmission--E1 line--(E1/CE1 interface) Router.