This Calculator Interface allows the TEKTRONIX: 31 to transmit graphic and alphanumeric information to a Computer Display terminal. The graphic data may be presented to the screen of the terminal as either light or dark vectors. Alphanumerics may be transmitted from the calculator and written on the screen of the terminal. Additionally, alphanumerics may be transmitted to the calculator for later rebroadcast (i.e. Leran Mode). All of the functions of the 31/10 Interface are programmable within the calculator. The Interface allows the terminal to be used in a dual-interface environment. The second interface installed within the terminal should be the Optional Data Com-munications Interface (TEKTRONIX: 021-0074-00). Switches on the front panel of the terminal then determine which interface is active. The Interface consists of a Logic card which plugs into the Terminal pedestal, a Receiver Card which mounts to the inside-back of the pedestal, and interconnecting cables. Provisions have been made to add optional features to the interface by adding an Option Card.