Abstract: A system for controlling and accounting for retrieval of data from a CD-ROM memory containing encrypted data files from which retrieval must be authorized. The system includes an authorization and key distribution terminal and a plurality of customer data retrieval terminals having such memories loaded therein. The authorization terminal authorizes retrieval of data by authorized customer terminals by providing to the authorized customer terminals an encryption key for enabling retrieval of the data and a authenticated credit signal for use in limiting the amount of data to be retrieved from the files. The encryption key is encrypted for communication to the customer terminals in unique unit keys that are stored in the respective customer terminals.

Abstract: A system for companding digital audio signal samples processes the digital audio signal samples to correct errors induced by the compression and expansion processes. These errors are calculated prior to compressing the samples. Such errors are calculated in accordance with a predetermined compression process and a predetermined expansion process; and the digital audio signal samples are corrected in accordance with such calculations prior to compression. The compression process includes providing a 3-bit gain word for a block of 70 samples. The gain word is computed in accordance with the position of the most significant "1" bit in the sample(s) having the peak magnitude. Each individual sample is processed in accordance with the block gain word to compress the sample by reducing the number of magnitude bits.

Abstract: A system in a subscriber television network for enabling descrambling of a received scrambled signal on a prepaid basis and/or an impulse-purchase basis. A received mask signal uniquely related to the scrambled signal is compared with a received authorization signal indicating whether the subscriber is authorized to receive the scrambled signal on a prepaid basis and a prepaid signal for enabling descrambling is provided when the compared signals match. A not-prepaid signal is provided when they do not match. A received cost signal indicating the charge for descrambling the scrambled signal and a received credit signal indicating the subscriber's endlessly accumulated credit are processed with reference to a stored record of the subscriber's prior accumulated charges to determine whether the subscriber has sufficient available credit to pay for descrambling of the scrambled signal.