Yes there is. Doing a "Hold on System" is another option. I haven't tried that with my 396T to know whether a "System Hold" is released when the scanner is powered down. I knew the system quick key thing would work, so that's why I suggested it.
Here is what the manual says on how to Hold on a System:
Holding On a System
To temporarily hold on a system, tap F. To hold on a different system, tap F then
rotate the control to select the system. Normal scanning resumes 2 seconds after
your last selection.
To permanently hold on a site or system, press and hold the Scroll Control for 2
seconds. f flashes in the display’s upper left corner. The scanner continues to
scan only the current system. To hold on a different site or system, rotate the
Scroll Control to select the new site or system then press [EYES].