Rembrandt's acquisition of U.S. patent No. 5,243,627 on signal interleaving is wrapped up in the confusing history of AT&T, Lucent Technologies, Paradyne and Globespan Technologies.
AT&T, which originally developed signal interleaving within Bell Labs, acquired Florida-based Paradyne Corp., a digital modulation specialist, in 1989. When the patent was issued in 1993, AT&T Paradyne was seen as the company's center of excellence in digital subscriber line technology. Paradyne was assigned rights to the interleaving patent as part of its portfolio of carrierless amplitude/phase modulation patents, which were used primarily in asymmetric DSL designs.
In 1996, the creation of Lucent Technologies out of what used to be AT&T Microelectronics caused a complex reassignment of those patents, at a time when the Globespan chip designs at Paradyne were being spun out into a separate company, Globespan Technologies, and Paradyne itself was being acquired by the Texas Pacific capital group. Two years ago, Zhone Technologies, an Oakland, Calif., telecom equipment supplier, bought Paradyne. It is not clear whether Paradyne still retained rights to the '627 patent--which had become one of the critical pieces of intellectual property for the digital modem--at that time.
