Abstract: A communication system communicates a high-speed clock or other balanced signal on the backs of two data signals by differentially modulating the data signals with the clock signal and communicating the two data signals in differential common mode form. The clock signal is extracted from the data signals at the receiving end of the system by applying the data signals to differential line receivers.

Abstract: A data stream is received by a first in a series of repeating devices and retransmitted from repeating device to repeating device. As the data stream is retransmitted, the data stream accumulates jitter. A jitter reduction apparatus therefore is used after a series of repeating devices to substantially reduce the accumulated jitter. The jitter reduction apparatus receives the data stream, stores the recognized data, then retransmits the data using a recovered clock signal. According to one embodiment, the recovered clock signal is the clock signal of the original data transmission. According to another embodiment, the recovered clock signal is derived from the data stream as input to the first of the series of repeating devices. Such derived clock signal serves as an estimate of the original data source clock signal. By using a recovered clock signal (e.g.

Abstract: Two message security methods and apparatus for the same for token ring local area networks. According to a first method, a port in a ring central controller examines the source and destination addresses of a received data packet and stores a received data packet and replaces the data portion with unrelated data bits only if the address does not match that of the attached user station. In another embodiment, the port scrambles the data portion of the received data packet if the addresses do not match.

Abstract: A security system for local area networks (LAN) to prevent eavesdropping of or to control access to LAN traffic at repeater or concentrator ports. The security system determines which repeater ports are to have security activated according to a given set of criteria. For ports with security activated, the contents of the data field of data frame transmitted from the repeater port to the local device are replaced with an arbitrary bit pattern.

Abstract: A security system for local area networks (LAN) to prevent eavesdropping of or to control access to LAN traffic at repeater or concentrator ports. The security system determines which repeater ports are to have security activated according to a given set of criteria. For ports with security activated, the contents of the data field of data frame transmitted from the repeater port to the local device are replaced with an arbitrary bit pattern.