What is it?
Samsung / Commodore SQ-1000 electronic typewriters can be modified to work as a teletype terminal. They use a simple 8bit microcontroller to scan the keyboard matrix and do the printing itself.
The keyboard was originally attached using a flat-flex connector directly to the mainboard. The connector was unsoldered and connected to an Arduino microcontroller, which emulates the keyboard matrix. Another arduino is connected to the keyboard and scans the matrix.
Both Arduinos use UART/RS-232 to either send/receive data from a serial connection.
Modified Commodore SQ-1000