Most large time-sharing computers require some sort of a data concentrator or multiplexor to accept inputs from a large number of low-speed remote terminals. Two major disadvantages of most of these concentrators are that they are nonprogrammable and relatively expensive. This paper describes the use of a small microprogrammed computer with a special instruction wired into the READ-ONLY memory to perform the multiplexing action. This approach has resulted in a programmable terminal controller which will handle up to 32 remotes, and provides enough processing capability to do code conversion and editing. This not only relieves the main computer of these routine tasks, but also reduces the amount and complexity of system modification within the main computer.