Abstract: A system for automatically providing hypertext for character strings of a text file at a content server. A central server provides central control of the links of text files of a plurality of content servers in an information network such as the Internet. The central server intermittently updates each content server with new character strings and/or destination addresses, such as Uniform Resource Locators (URLs). The content servers also update the central server with new character strings. Optionally, each content server can query the central server on a real-time basis to obtain a destination address for a character string which does not have a corresponding valid destination address. The central server responds to such queries by searching its master databases, and using a search engine if required. Hit count data is maintained at the content servers and transmitted to the central server intermittently.

Abstract: Data are added invisibly to the active video component of a television signal by a modulated carrier. The data, upon recovery, may be used for numerous purposes, including network signaling, data transmission, program identification, remote machine control, broadcast verification, and signal quality detection and measurement.

Abstract: A method for timing audio and video component signals of a television signal with coincidental markers generates a field pulse every Nth field of the televison signal at the transmitter. The duration of the field pulse is approximately one video field, and is ued to enable an audio tone generator for the one video field and to switch a distinctive video signal, such as a flat video signal, into the video component signal for the one video field. At the receiver the two component signals are input through a synchronizer to a waveform display device, such as an oscilloscope, to observe the time differential between the two markers in the audio and video component signals. The audio component signal is delayed by the synchronizer until the markers are again in time conicidence as at the transmitter.