What technical adjustment is necessary to increase receptor exposure when using automatic exposure control (AEC)?

To increase receptor exposure when utilizing automatic exposure control (AEC), adjusting the density setting is the appropriate measure. The density setting allows the radiographer to influence the amount of exposure that the AEC system will provide to the receptor before terminating the exposure. By increasing the density setting, the AEC system responds by allowing for a longer exposure time or a higher degree of exposure to the receptor, thus enhancing the overall receptor exposure.

The other options do not directly address the AEC's intrinsic functioning. Increasing milliamperage affects the quantity of x-ray photons produced but does not directly interact with AEC settings. Decreasing kilovoltage can lead to lower overall energy of the photons, which may not necessarily enhance receptor exposure, especially if the desired image quality requires a specific kVp level. Finally, decreasing the backup timer can reduce the maximum exposure time allowed but does not inherently increase receptor exposure; instead, it might risk underexposure by limiting the time the AEC has to reach the desired exposure level. Therefore, increasing the density setting directly modifies the criteria by which the AEC compensates for exposure, making it the correct choice to increase receptor exposure.