Unfortunately, playing a CD in a car is anything but ideal. If enough road vibration gets past the player's suspension, the tracking servo can't drive the pickup smoothly and the player will "skip". If the disc has surface scratches or imperfections, not enough light is reflected back from the disc to drive the focus servo. If the sound pressure level in the car is very high, the sound can excite the disc into resonance, reeking havoc with the focus servo.

Of course, a servo's gain can be increased to improve performance, but high gain settings tend to make the servos work against each other. That's why a CD player with very high vibration resistance can't tolerate dirty discs, and a CD player that can play even damaged discs tends to skip with road vibration. To compensate for the changing conditions in a car, Sony's unique Active Servo Control (ASC) provides real-time monitoring and adjustment of the laser servos. As the disc is read, the laser's reflection is analyzed and the data is evaluated for errors. If scratches or dirt reduce the reflection, the focus servo's gain is increased so the laser can read through the imperfections. If the tracking signal begins to show a large error percentage, the system increases the tracking servo's gain to maintain stable operation.

With the balance between focus and tracking gains constantly evaluated, the player's performance is always optimized. The effect of ASC is pretty amazing-hit a rough road and the player immediately turns up the tracking gain to handle the problem. Run into a bad part of the disc and the player "learns" the condition, turns up the gain and plays right through most problems! ASC brings a new level of reliable operation to the world of CD players.