Abstract: Methods and apparatus for transmitting and receiving data using framing circuitry designed to generate data frames of a first duration at a first data rate. According to the invention, data frames are generated and decomposed at lower data rates than the rate for which the framing circuitry was originally designed, i.e., the first data rate. The framing circuitry is programmed to organize a data stream into a sequence of data frames of the first duration or to decompose such data frames into a data stream. According to the invention, such a sequence of data frames corresponds to a selected one of a plurality of equivalent data rates. Each of the equivalent data rates are lower than the first data rate.

Abstract: A Scalable Multimedia Network providing integrated networking of data, voice, video and image services over a variety of access facilities including metallic loops, fiber/coax or digital fiber is disclosed herein. The SMN establishes customer initiated switched virtual circuits for all traffic types and directs them to the appropriate backbone network. The SMN is based on a distributed switching platform that includes a protocol adaptation capability which permits communications between customer premises equipment and potentially incompatible backbone networks or network servers.

Abstract: An ADSL modem provides compensation for a nonlinear telephone impedance by predistorting transmit signals such that the voltage across the nonlinear impedance is correct independent of the impedance. Correcting the voltage across the nonlinear impedance reduces noise in the telephone due to intermodulation products generated in the voice band. The modem comprises a transmitter that includes (a) a signal source providing a source data signal and (b) a predistortion circuit for predistorting the source data signal to provide a modem transmit signal for coupling to a transmission loop having a nonlinear impedance coupled thereto. The modem device further includes a receiver for receiving a modem receive signal from the transmission loop. The source data signal comprises source digital words, each source digital word corresponding to a particular voltage level.

Abstract: A Scalable Multimedia Network providing integrated networking of data, voice, video and image services over a variety of access facilities including metallic loops, fiber/coax or digital fiber is disclosed herein. The SMN provides a broadcast switch using a tiered system of buses. Channel units are made to interface to a bus of any tier depending on bandwidth requirements of the particular channel units. The SMN is based on a distributed switching platform that enables carriers to economically provide service to a small number of customers and add capacity incrementally as the customer base increases. The platform has a protocol adaptation capability which permits communications between customer premises equipment and potentially incompatible backbone networks or network servers.

Abstract: A scalable Multimedia Network providing integrated networking of data, voice, video and image services over a variety of access facilities including metallic loops, fiber/coax or digital fiber is disclosed herein.The SMN establishes customer initiated switched virtual circuits for all traffic types and directs them to the appropriate backbone network. The SMN is based on a distributed switching platform that enables carriers to economically provide service to a small number of customers and add capacity incrementally as the customer base increases. The platform has a protocol adaptation capability which permits communications between customer premises equipment and potentially incompatible backbone networks or network servers.

Abstract: A Scalable Multimedia Network providing integrated networking of data, voice, video and image services over a variety of access facilities including metallic loops, fiber/coax or digital fiber is disclosed herein.The SMN establishes customer initiated switched virtual circuits for all traffic types and directs them to the appropriate backbone network. The SMN is based on a distributed switching platform that enables carriers to economically provide service to a small number of customers and add capacity incrementally as the customer base increases. The platform has a protocol adaptation capability which permits communications between customer premises equipment and potentially incompatible backbone networks or network servers.

Abstract: An interface circuit is provided for implementing zero-byte substitution (ZBS) in a channel unit or line card which couples a digital subscriber line, such as a basic or primary rate Integrated Services Digital Network (ISDN) line, to a T1 network or other digital transmission facility. On the transmit side, the occurrence of an all-zero data byte in a B channel of the ISDN interface causes a corresponding zero byte indicator (ZBI) flag to be produced in the D+ channel, and also causes the all-zero byte to be replaced by the preceding non-zero data byte rather than by a prescribed or predetermined data byte. On the receive side, the occurrence of a repeated data byte in a B channel is detected and causes the current data byte to be replaced by an all-zero byte to restore the original data. The ZBI flag is then used as an error check bit to verify that the reinsertion of the all-zero byte was correct.

Abstract: A Scalable Multimedia Network providing integrated networking of data, voice, video and image services over a variety of access facilities including metallic loops, fiber/coax or digital fiber is disclosed herein. The SMN establishes customer initiated switched virtual circuits for all traffic types and directs them to the appropriate backbone network. The SMN is based on a distributed switching platform that enables carriers to economically provide service to a small number of customers and add capacity incrementally as the customer base increases. The platform has a protocol adaptation capability which permits communications between customer premises equipment and potentially incompatible backbone networks or network servers.

Abstract: A Scalable Multimedia Network providing integrated networking of data, voice, video and image services over a variety of access facilities including metallic loops, fiber/coax or digital fiber is disclosed herein.The SMN establishes customer initiated switched virtual circuits for all traffic types and directs them to the appropriate backbone network. The SMN is based on a distributed switching platform that enables carriers to economically provide service to a small number of customers and add capacity incrementally as the customer base increases. The platform has a protocol adaptation capability which permits communications between customer premises equipment and potentially incompatible backbone networks or network servers.

Abstract: Loop circuits lacking byte alignment are tested by test equipment signals at 9.6 kbps transmitted over a DS.phi. format 19.2 kbps communication network. Upon indication of loss of 19.2 kbps framing, return signals from the loop are reformatted into a 9.6 kbps format by selecting proper return bytes using a logic system stored in an office channel unit (OCU).

Abstract: In a telecommunication system, a circuit is provided for determining the system mode and for restoring converted signalling bits. The circuit is designed to be used in a telecommunication system that lacks frame alignment. The circuit may serve as an trunk line interface located in a Direct Digital Access Office Channel Unit. Alternatively, the circuit may be coupled to a single trunk line which links Customer Premises Equipment (CPE) to the telecommunication system. The detection portion of the circuit determines the system mode of the trunk line connected to a CPE by detecting signalling bits when frame alignment is not maintained. The restoration portion of the circuit restores signalling bits which were converted due to a lack of frame alignment to their pre-converted state.

Abstract: In a transmission system, adding and/or dropping any one or more of a plurality of digital signals of one or more digital transmission bit rates is facilitated by employing a unique transmission signal in which data words associated with individual digital signals are arranged in prescribed groups. The transmission signal data word groups are obtained by formatting the individual digital signals to be combined into a unique channel frame format common to all of the digital signals and by employing a unique one-step multiplexing process to insert digital words from the channel frames into the group of data word positions in the transmission signal associated with the particular signal being combined. Consequently, digital signals may be added to the transmission signal by formatting them into the common channel frame format and, then, inserting the digital words therefrom in the one-step multiplexing process into an associated group of data words positions in the transmission signal.

Abstract: Method and apparatus for looping around a digital transmission line (150) at a predetermined channel unit (172) to test the line from either end of the line. Each channel unit in the line is responsive to a first and a second received control code to perform one of two operations. When the first and second received control codes are both first predetermined control codes from one end of the line, the data channel assumes a state to pass the second received first control code and any subsequently received control codes to the next channel unit. However, when the first and second received control codes are first and second predetermined control codes from the one end of the line, respectively, the data channel unit connects the transmit path from the one line end to the receive path back to the one line end, thus looping back to the digital transmission line.

Abstract: A channel unit (172) for looping around a digital transmission line (150) in response to first and second received control codes. When the first and second received control codes are both first predetermined control codes from one end of the line, the data channel assumes a state to pass the second received first control code and any subsequently received control codes to the next channel unit. However, when the first and second received control codes are first and second predetermined control codes from the one end of the line, respectively, the data channel unit connects the transmit path from the one line end to the receive path back to the one line end, thus looping back the digital transmission line.

Abstract: The most significant bits of each input word of a linear PCM signal address a read-only memory (ROM). Stored at each ROM address is a table of instruction words, one instruction word for each bit in the output word. The instruction words direct a switch to select each bit for the output word from a choice of 1, 0, or an input bit PCM compression according to a predetermined characteristic is implemented by instruction words which direct selection of the proper chord bits from 1 or 0 and the proper step bits from the input bits. A different compression characteristic may be implemented by a different set of stored instruction words. The instruction words also command selective bit inversion and selective inclusion of the bit in a parity check. Implementation of the translator with commercially available hardware is described.

Abstract: An audio program signal is converted into 12-bit PCM words and two 12-bit words are inserted into three 8-bit time slots in a T1 line. To avoid interference from a "yellow" alarm in which the second bit positions of all of the 8-bit time slots are pre-empted, the three least significant bits are placed in the second, sixth and tenth bit positions of the 12-bit words, which alone can occupy the second bit position of the 8-bit time slots.A translator for generating the 12-bit words from 14-bit linear PCM words is described. The six most significant bits of the 14-bit words address a ROM. Stored at each address in the ROM is a table of twelve instruction words. Each instruction word causes a selector switch to choose a bit of the output word from 1, 0 or an input bit. Bit order of the 12-bit words is therefore controlled by the order of instruction words in the tables of the ROM.