Abstract: In one embodiment of the invention, a conventional home computer is connected via the Internet to a link broadcasting computer that is being accessed by many other households. The link broadcasting computer receives the same television signals (including ATVEF signals or other datacast signals) received by the home televisions of the various users. The link broadcasting computer detects the ATVEF signals embedded in the vertical blanking interval of each television channel and communicates to each user's home computer only the ATVEF information for the particular television channel(s) previously identified by the user. The user can then access a website identified by the information. Various options are further described herein.

Abstract: An automatic gain control circuit in the feedback path for a laser wavelength control circuit is described herein. This gain control circuit automatically adjusts the amplification of the analog signals output from a photodetector array, where the array detects a fringe pattern created by a laser beam. Another feature of the preferred embodiment feedback circuit is the automatic setting of a DC offset voltage that compensates for errors in the feedback path and enables an accurate determination of a dark level signal in the fringe pattern signal. This dark level signal provides a reference for measuring the magnitude of the fringe pattern signal. Varying photodetector outputs may now be more accurately measured. The preferred embodiment feedback circuit also employs a very fast amplifier anti-saturation circuit using LED's connected in a clamp circuit.

Abstract: An audiovisual subscription system includes means for aperiodically inverting the lines of a transmitted video signal of a frame-by-frame basis and for decrypting encrypted PCM audio information which is transmitted along with the aperiodically inverted video information.