Listen (16-bit) is a data link monitor designed to assist in the debugging and troubleshooting of serial communications links. The program uses standard Windows COM port drivers to tap into RS-232 transmit signals for monitoring bi-directional communications between two devices. Data is captured and displayed in real-time, using custom defined character fonts and colors. Filters may be applied to the data and a trap buffer, triggered on a character string comparitor, may be used to isolate intermittent faults. One of the unique features of Listen is its ability to display non-printing characters in a variety of formats to suit the user. Each character may be overridden to display a unique text string representing its value.