Realistic 120-1959 - Manual (Page 3)

. . . we strongly urge you to have this unit installed by a
professional auto sound installer.
Choosing The Mounting Location
We suggest that you connect the wiring and confirm that the equalizer/
booster operates properly with your system before you actually mount it in
your vehicle. However, you should choose the mounting location first.
Then, when the unit is connected and working properly, you can mount it
without re-routing the wires.
Choose a mounting location below the dash that:
Is as near as possible to your vehicle's radio, tape player, or other
main auto sound component.
Does not interfere with operation of the vehicle.
Is not directly in front of a heating vent.
Allows drilling of mounting holes, without damaging other vehicle
components.
Allows enough leg room for passengers.
Allows convenient and safe routing of wires.
Then, connect the wiring as follows with the equalizer/booster as close as
possible to the chosen location.
Wiring Connections
CAUTION: If the wiring harness (for power and speakers) on your older
existing radio/tape player is not compatible with your new
RadioShack equalizer/booster's wiring harness, we suggest that
you modify the existing wiring using adapters available at your
local RadioShack store. Or, you can have a qualified technician
modify the older wiring for you. Modification of your new
RadioShack unit will void its warranty.
Connecting Power/Speakers to the Equalizer/Booster
1. Before you make any connections, disconnect the positive (+) wire from
your vehicle's battery. This reduces the possibility of damage to your
system during installation.