The conductors in each layer are separate, so that the capacitance of each one can be measured separately. As with a resistive panel, the conductors run at right angles to each other, so that the device can sense an X and a Y position when touched. The difference is that the separate conductors are scanned in rapid sequence, so that all the possible intersections are measured many times per second.

When you touch the screen with your finger, it steals a little of the charge from each layer of conductors at that point. The electrical charge involved is tiny, which is why you don't feel any shock when you touch the screen, but this little change is enough to be measured. Because each conductor is checked separately, it is possible to identify multiple simultaneous touch points.

Pro-cap technology is not without its challenges. The system of conductors is susceptible to electrical noise from electromagnetic interference (EMI). This can be a problem for display devices such as LCD and OLED panels that rely on an active matrix backplane of transistors to rapidly switch the individual subpixels on and off. The touch screen controller must be able to filter out this background noise and figure out which signals are from actual touch points.

The controller is often asked to make other decisions as well. Comparing results from adjacent coordinates can help determine if the touch is hard or soft, or if it is the result of the palm of the hand resting on the screen and thus should be ignored. Some smartphones rely on the touch screen to signal when the phone is being held next to the user's face, so that the screen can be turned off to save power.

All these tasks require significant processing power, which makes the controller more expensive. In addition, the touch screen only works when you apply a conductor; the ball of your finger works, but not your fingernail. Some pro-cap screens will work even if you're wearing thin surgical gloves, but they won't work if you have thick winter gloves on. (The exception is if the gloves themselves are conductive; you can buy gloves with conductors woven into the fingertips so that they can conduct the charge from the screen to your finger.)