Radio Shack TRS-80 Model II Reference Manual page 65

Library Commands
DUAL
Duplicate Output to Video and Printer
This command causes all video output to be copied to the printer, and all printer
output to be copied to the display.
Notes:
1. Printer and display output may be different, due to intrinsic differences in the
output devices and in the output software.
2. Having dual routing on will slow dowri the video output process.
3. If your printer is currently off-line or not powered-up the Video Display will
appear to be outputting about one character every three seconds (30 seconds if
you have run the
LPII
patch file). You should turn off
DUAL
or ready your printer
to remedy this.
Sample Use
For a hard copy of all the system/operator dialog, turn on
DUAL:
DUALON
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