Most terminals have an auxiliary port that can be connected to a serial printer. When this port is configured as a transparent printer port, print jobs may be run simultaneously with normal terminal operation.
Data bound for the printer is preceded by a terminal escape sequence that turns on transparent printing, and is followed by a sequence that turns transparent printing off.
Transparent printer devices are created in /dev and, after configuration, are accessed in the same manner as a printer on a regular serial port. Data sent to a transparent printer device is automatically "wrapped" in the transparent print on/off command strings for the specified printer.