A set of hardware modules collectively called the research device coupler (RDC) has been designed to bring instrumentation interfacing capability to scientists using interactive terminal-oriented systems. The scientist familiar with APL, Fortran, PL/1, or Basic may now exercise the digital and analog I/O facilities of the RDC using these high-level languages. The RDC is an ensemble of modular I/O units with built-in functions which act with, or as, a terminal. Its primary distinction is that it takes advantage of existing interactive systems without need for change either to the host system hardware or software or to the user's terminal. © 1975, IEEE. All rights reserved.