Abstract: A cordless telephone system achieves synchronism for each one of multiple portable units to the same communication channel for communicating with a common base unit. The cordless system uses a dual channel process to allow both the freedom to dynamically change channels as needed to avoid interference while simultaneously providing a capability to resynchronize any portable unit with the base unit on a selected active channel. This is achieved through the use of a fixed service channel and an active channel which changes as needed. If a channel change is made during a call, after the call is completed, the base unit returns to the previous active channel and broadcasts a message to the multiple portable units indicative of the new active channel. Also, any portable unit that attempts to communicate with the base unit on the wrong channel and fails to get a response will transmit a message on the fixed service channel requesting the current active channel from the base unit.

Abstract: A cordless telephone system includes an arrangement wherein multiple portable units operate with a common base unit using the same security code without conflict or confusion. When a portable unit attempts to establish a radio link with the base unit, for example, this originating portable unit generates a random number which is retained by this unit and also transmitted to the base unit. This random number is substituted for the common stored security code, then shared by the base unit and all of the portable units, for creating a temporary unique security code that is known only to the base unit and the originating portable unit. Interference from other portable units attempting to gain access to the base unit while the originating portable unit is actively communicating with the base unit is thereby advantageously prevented.

Abstract: The disclosure relates to an apparatus and method for creating digital signatures from frames of selected video segments such as TV commercials by a digitizing, compression and selection process which produces a multi-digit signature from each frame. The signatures are stored in a memory database. In the recognition mode broadcast video transmissions are similarly digitized frame by frame to generate signatures which are then compared with the signatures in the database to find matches. The system cycles efficiently through the database testing for signature matches and then totalizing the signature matches to determine occurrences of a match between a transmitted segment or commercial and a stored segment or commercial. The system also includes signature generating and comparison circuits which permit wide variations in the quality of the input video signals form a variety of different media sources such as off-air, videotape or camera inputs while maintaining accurate recognition.