Tandy 1000 SL Technical Reference Manual page 571

Software
CPrSc
SysRq
Tells MS-DOS to direct console output to both the printer
and the console. A second CPrSc halts printer output.
Interrupts the current process and allows another program
to take control, if supported. When the SysRq key is
pressed, INT 15H is invoked with AX=8500H. When the
key is released, INT 15H is invoked with AX
=
8501H.
Reset Restarts your computer.
50.