Modem eliminators.

Modem eliminators

One modem eliminator can connect a local terminal and computer port in lieu of the pair of modems they would normally connect to. Plus, a modem eliminator enables DCE-to-DTE data and control-signal connections that are not easily achieved by standard cables or connectors in a synchronous environment.

Basically, a modem eliminator simulates a sync data link. It does this two ways: First, it provides clocking, which is mandatory for sync devices to communicate. Second, it provides the handshaking that DCEs do.