We use such a link to connect a terminal (or a micro's COM port) to a CAMTEC X25 PAD, located at the patch centre ("PAD" stands for Packet Assembler-Disassembler, as usual). Dedicated connections from a terminal to a specific computer are used in a few cases (e.g computer operators). Normally, apart from signal-return, only the data transmit and receive lines are used, and the terminal-ready control line DTR (optional), accounting for four of the eight available wires. In situations which call for additional control lines to be used, one would either allocate some of the unused wires to them, or install short-haul modems at each end to provide full 'hardware handshaking'. As a terminal connection method, no automatic error recovery is provided: this isn't a major problem for us in practice.
The Nuclear Structure group have their own DECservers, which they operate in an analogous way.