Abstract: A system for determining the data bits represented by the received symbols of one or more data constellations includes converting the received symbols into multi-bit values (preferably in two's complement form), selecting a number of the most significant bits of each of the multi-bit values and inverting the most significant bit thereof to derive the data bits represented by the respective symbol.

Abstract: A synchronous demodulator is controlled by a phase locked loop for tuning to a pilot in a television signal. A start-up interval is commenced upon initiation of tuning (either after power-up or a channel change) during which a substitute signal at the pilot frequency is supplied to the phase locked loop to rapidly bring the VCO close to its lock-up frequency. Thereafter the IF signal is supplied. The start-up interval is defined by an AFC Defeat signal from a microprocessor and controls an IF switch. The substitute signal is from a crystal oscillator.

Abstract: A circuit for error correcting a received complex data signal comprises a synchronous detector for recovering an in-phase data component from the received signal and a Hilbert transform filter for estimating the related quadrature component from the recovered in-phase data component, the recovered in-phase data component including a periodically recurring reference signal. A decision feedback loop is periodically operable in response to the reference signal for initially error correcting a selected characteristic of the received signal at a first relatively rapid rate and for subsequently error correcting the selected characteristic at a rate which is less than the first rate and which is dependent upon the estimated S/N ratio of the received signal. In one embodiment, phase errors are corrected at a rate which is also directly related to the value of the estimated quadrature component. In another embodiment, amplitude errors, e.g.

Abstract: A video decoder includes an application specific integrated circuit (ASIC) that has the decoder address and a secure decryption key stored in a one-time-programmable memory. Encrypted messages are received and selectively supplied to a packet decrypter and to a video decrypter based upon the location of bits in the message string. The packet decrypter is responsive to a flag in the packet data for utilizing a secure key or a unsecure key for decryption of the packet data. The information derived from the secure decryption and the secure key itself are never available (or ascertainable) outside of the ASIC. Only information concerning the unsecure key is available outside of the integrated circuit.

Abstract: A restrictive access control system includes a 3-state switch for controlling the operating mode of the system and limiting tuning access to only designated channels. Tuning information is provided to a microprocessor via a control panel keyboard for storage in a nonvolatile memory and for subsequent recall therefrom when desired channel information is entered in the control panel by a viewer. In one embodiment, a 3-position key actuated switch has a first OFF position, a second PROGRAM position, and a third ON position. In the ON and OFF positions, the key may be removed from the switch while in the second PROGRAM position the key may not be removed from the switch. Programming of the nonvolatile memory may only be accomplished with the key in second PROGRAM position for storing either desired channels or locking out undesired channels.

Abstract: A tilt correction circuit for a color television signal processor includes a differential amplifier having a first tuned circuit tuned near the color carrier frequency and a second tuned circuit tuned near the picture carrier frequency. An IF video input signal is applied to the differential amplifier, the output of which reflects the relative effect of the two tuned circuits. A correction voltage is derived by peak detecting the color burst and comparing it with a reference voltage related to a nominal color burst level in a color television signal. The correction voltage is supplied to the other input of the differential amplifier to change the relative effects of the tuned circuits to adjust the frequency response over the IF band. A tilt defeat circuit is included for disabling the correction voltage where the magnitude of the correction voltage indicates the presence of a monochrome signal.