Abstract: In a local area network all communication nodes are connected only to a centrally located star network coupler, but data is transmitted from one communication node to the next active communication node in a sequence defined by a ring protocol. The star network coupler may be implemented by switches capable of connecting a receiver for one communication node to a transmitter for the next communication node or to a bypass line for the next communication node. However, preferably the star network coupler comprises a selective multiplexer for each of the nodes. Each selective multiplexer has inputs connected to all of the communication nodes to receive therefrom transmission data and a line status signal indicating communication activity with each node so that inactive nodes can be bypassed.

Abstract: A system and method for recovering a clock signal from digital data signals which do not include a separate clock signal. The system and method detect transitions from one logic state to the other logic state in the digital data signal, and compare the time alignment of these logic state transitions to an input clock signal from a voltage controlled oscillator. A correction control signal is generated as a function of the time alignment of the digital data signal transition with the input clock signal, and applied to the oscillator to vary the frequency of the clock signal as a function of the correction control signal, whereby a digital data recovered clock signal is aligned with the digital data signal.

Abstract: An arrangement for a speech enhancement processor which maintains the processed speech at a constant level regardless of large changes in the associated noise level. The composite speech and noise signal is applied to a first AGC circuit and then to a speech enhancement system which removes tonal, impulse, and wideband noises from the signal. The extracted noise power estimates are subtracted from the constant amplitude signal to provide a gain control signal value to which the gain of a second variable gain amplifier is inversely proportional. The amplifier multiplies the processed speech output from the enhancement system and, because of the variable gain control, provides an output speech signal having short-term amplitude levels which correspond to those of the input speech signal, and having a constant long-term amplitude level.

Abstract: A digital communication system employs a technique of effectively controlling the size of the bytes making up a field of data to be serially transmitted from one station to another, particularly one wherein the byte size may be selectively changed during the transmission of the data field. Assembly of a transmitted data field is controlled so that it includes an encoded data byte, termed a first pre-header byte, which contains information as to whether or not a change in the byte size of the data field is to occur. If the first pre-header byte indicates the occurrence of a byte size change, it also will contain a code representative of the size of the change. In addition, for a change in byte size, a second encoded data byte, termed a second pre-header or count byte is generated and immediately follows the first pre-header byte. The count byte contains information which specifies the length of that portion of the data field which precedes the occurrence of the change in byte size.

Abstract: Communications between processor terminals are carried out through the use of communication adapters. Each adapter receives selected control signals for transmitting or receiving data over a serial communication link to or from a remote terminal. The transmission portion of an adapter includes pretransmission control circuitry which receives control signals and stores transmission control signals which are used to control the format and serial transmission of a frame of data to a remote terminal. Each frame of data is begun and terminated with a uniquely encoded flag byte. Following the first flag byte are successive address and control fields. An optional information field may follow the control field and may include encoded information designating a dynamic change in the byte size of the data.

Abstract: A technique and implementation of generating and supplying synchronization and error checking signals to a serially transmitted data stream includes the generation of flag bytes which define the end boundaries of the serial data stream, an abort character for aborting the transmission of a frame of data in response to certain conditions, and a diagnostic evaluation character inserted into the data stream. In addition, the invention provides a technique for ensuring that the unique binary code by which a flag byte is defined occurs in the transmitted data stream only where intended. The flag code has been chosen to contain a prescribed number of consecutive one bits, (i.e. -- six) flanked by zeroes, and circuitry monitors the contents of a data frame as it is being serialized out for transmission to a remote terminal at times other than during flag transmission.