Need to drive a DC motor!

I have a request, it's
urgent, cause my undergrad project depends on it. (So,
please reply fast).
I am working on a project in robotics and my
branch is Computer Science. I require a circuit idea
for controlling a 12V, 500mA DC servo motor. I am
reusing a receiver circuit of an RC toy car. Which
provides me with two terminals with voltage varying
between +4.5,0,-4.5 volts.( The two terminals provide
positve voltage with respect to common ground)
All I need is to drive the Servo motor, with direction control provided by the two terminals and common ground, without any
form of speed control or braking. I am using a 12v
lead acid battery for the servo and AA size batteries
for the RC circuit. If you need any further
information, please mail me on this address.

Waiting for a reply,
Regards,
Ashish Narain
Project Leader,
NaviACE.

P.S. I am not using any PWM signal, just driving the servo as any other DC motor (using it mainly for the high torque).

Hi,
Since you have the control circuit ready with you, all you need is a H-BRIDGE which can run your motor in either direction.
Look at these pages:
http://www.armory.com/~rstevew/Public/Motors/H-Bridges/Blanchard/h-bridge.htm
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