Optimus 120-2117 - Manual (Page 12)

1. Disconnect the cable from your vehicle's negative (-) battery terminal
2. To open either fuse holder, unlatch the two latches on the fuse holder
until it springs apart.
3. Then slide off the metal holder on each end of the fuse and remove the
fuse.
4. If the fuse is blown, replace it. Use only standard 1-1/4 inch fuses
with the proper rating. The red +12 TO IGNITION wire's fuse must be 3
amps. The yellow +12V TO BATTERY wire's fuse must be 0.5 amps.
CAUTION: The supplied spare fuses have the correct rating. If you
use a fuse with an incorrect rating, the stereo could be
damaged.
5. Reassemble the fuse holder by squeezing it together until it latches.
6. Reconnect the cable to the vehicle's negative (-) battery terminal.
The FCC Wants You To Know
Your stereo might cause TV or radio interference even when it is operating
properly. To determine whether your stereo is causing the interference,
turn off your stereo. If the interference goes away, your stereo is
causing the interference. Try to eliminate the interference by:
Moving your receiver away from the stereo.
Contacting your local RadioShack store for help.
If you cannot eliminate the interference, the FCC requires that you stop
using your stereo.