Abstract: In a terminal adapter which is located between a data terminal equipment unit (11) and a data communication network (12) and which includes a buffer memory (22, 27) for memorizing an original data signal sequence sent from each of the data terminal equipment unit and the data communication network, the original data signal sequence is subjected to data compression by a data compression circuit to be thereafter memorized into the buffer memory and to be read out of the buffer memory as a readout data signal sequence. The readout data signal sequence is expanded by a data expansion circuit (32, 35) to be sent to the data terminal equipment unit or the data communication network at a transmission rate matched therewith. The data compression may be executed by the use of an LZ method, a modified LZ method, such as LZW, LZSS, or the like.

Abstract: A parallel interface is provided between a standard parallel port of a computer system and a modem so as to increase the data transfer rate between the two systems without modifying the hardware of the computer system and independently of the application program running on the computer system.

Abstract: A processor controlled test set is disclosed for testing special service circuits of a telecommunication system. A microprocessor controls the overall operation of the test set, while a digital signal processor provides high speed timing signals to the various test circuits for generating the wave forms used in testing, as well as analyzes the test result signals that are converted into digital signals. A calibration of the test generator signals as well as the signal measuring path is carried out prior to the test sequence. The digital signal processor also provides gain control over a talking path to maintain stability thereof. An I/O circuit of the test set provides plural communication paths between remote equipment and the test set to initiate and carry out various tests. Processors in the I/O module are effective to convert the various protocols of the serial data, by way of software, to digital bit streams usable by the test set.

Abstract: A method and apparatus for negotiating service configuration in a digital communication system is disclosed. In an exemplary embodiment the service negotiation system is implemented in a wireless spread spectrum communication system. The service configuration comprises data rates, frame formats and types of services. Types of service may include speech encoding, facsimile or digital data services. Further described herein is a digital transmitter and receiver using the service negotiation system to provide service configuration mutually acceptable at both ends of a communication link.

Abstract: A high speed teleconferencing apparatus and method, the apparatus including interface means for receiving a first analog signal and outputting a first digital signal, encoding means for encoding and compressing the first digital signal to produce a first compressed encoded signal, multiplexing/demultipexing means for receiving and splitting the first compressed encoded signal into at least two split compressed encoded signals, at least two converting means for receiving a respective one of the at least two split first compressed encoded signals and respectively producing at least two first synchronous signals, and at least two CCIT units for receiving a respective one of the at least tow synchronous signals and respectively outputting at least two high speed first synchronous signals to a high speed data link.

Abstract: A method adapts the amount of messages with a number of various identities transferred between a transmitter and a receiver. The transfer is accomplished in such a way that no essential information is lost even if the message rate from the transmitter exceeds the possible transfer rate. A data area is created in which each message with a certain identity is stored while awaiting to be transferred. When a new message with the same identity as an earlier stored message is supplied to the data area, the new message replaces the earlier stored message. The messages stored in the data area are scanned and are transferred to the receiver at a rate which is adapted to the rate possible for the transfer.

Abstract: Apparatus for governing information transfer among a plurality of data utilization elements, without rate oscillation, which apparatus is operative according to a rate based transport protocol having apparatus for determining the rate of information transfer between data utilization elements.

Abstract: A system and method for data transfer. The system determines the baud rate of a plurality channels carrying of asynchronous data streams by measuring a time period T between the beginning of a start bit and the transition to a logic high at the beginning of each odd-ASCII character. The system assesses baud rates over a continuous variable range. The system loops back data to its source to provide an echo while determining the baud rate.

Abstract: An apparatus and method for transmission of data. A four bit data word is converted into an eight bit code word having a run-length of (0,1) which includes four binary ones and four binary zeros is defined where the start and end bits comprise a 01 or 10 pair to ensure the (1,0) run-length across word boundaries. A hashing code is used to generate the code words and decode received code words.

Abstract: On converting an input data signal having a first transmission rate into an output data signal having a second transmission rate different from the first transmission rate, the input data signal is memorized as a memorized input data signal a first memory. A read clock generating circuit generates a read clock signal to read the memorized input data signal as a read data signal out of the first memory. A read control circuit controls the read clock generating circuit to stop generation of the read clock signal in order to make the read data signal have an overhead bit slot at a predetermined period. A rate control circuit produces a rate control signal having a predetermined pattern and an inhibit signal in accordance with the rate control signal. The read clock generating circuit stops generation of the read clock signal in response to the inhibit signal. A multiplexing circuit multiplexes an information signal to the read data signal on the basis of the rate control signal to produce the output data signal.

Abstract: A data communication system comprises a main device with a first microcomputer and an operating device with a second microcomputer. The devices are connected to each other by a first wire and by a second wire. In addition to that, input interrupt terminals of both devices are connected to the second wire. One device starts the sending of data by pulling the second wire to a first level, the detection of this by the other device is signalled back via the first wire and both devices then start an internal timer. When a predetermined time, corresponding to a data item to be sent, has lapsed the sending device pulls the second line again to the first level. This is detected by the other device, which measures the lapsed time and which uses this time to determine the data item sent by consulting preset conversion rules, that give a relation between time and a data element.

Abstract: A method and apparatus is provided for facilitating coherent communication reception. A received reference symbol coded spread spectrum communication signal is despread with a spreading code to derive a stream of reference samples and a stream of data samples. The channel response is estimated by utilizing the stream of reference samples. An offset frequency detector determines an offset to be applied to the received signal via a frequency locked loop, while a timing control compensates for slow timing drift and fast fading based on power estimates derived from the stream of reference samples and/or the stream of data samples. A rate estimator determines the rate at which the information was encoded, and the rate information is used to optimize the timing control, frequency offset detector and channel estimator. Thus an improved detection of estimated data symbols from the stream of received data samples is provided.

Abstract: A transmission and receiving system, includes a transmit interface unit, a transmit signal processing unit, a transmit signal converting unit and a microwave transmitting unit all a first location. The system further includes a microwave receiving unit, a receive signal converting unit and a second signal processing unit. The system can transmit information such as an audio/video signal of broadcast quality or file information via satellite from anywhere in the world to anywhere in the world (except the polar caps) in real time.

Abstract: A method and apparatus for a circuit physically realizing a Universal Asynchronous Receive/Transmit (UART) circuit 31, 40 having an automatic flow control feature. A preferred embodiment includes a UART 31 provided with additional control circuitry 39, 34 for automatically pausing transfers from the transmit data circuitry 35, 32 in response to a transition at the CTS (Clear to Send) input, and further provided with control circuitry 39 for automatically asserting and deasserting a RTS (Ready to Send) output when a receiver data threshold is reached.

Abstract: An interface method and device in a digital signal processing system which stores digital data regenerated from a recording unit in a memory, reads the digital data from the memory in response to a data transmission request signal of an object interface part, and transmits the read digital data to the object interface part in units of sound groups and also transmits channel classification data of 1 byte to classify the channel of the transmitted data together with the digital data to the object interface part.

Abstract: A convolutional encoder may be accomplished by providing a first register, a plurality of logic gates, a sampler, a second register, and a sequencer. In operation, the first register receives digital information at a code rate which convolutionally encoded by the plurality of logic gates to produce, based on the code rate, encoded samples. The sampler extracts the encoded samples at an extraction rate and provides them to the second register. To control this operation, the sequencer generates the code rate and the extraction rate based on a count value.

Abstract: The present invention relates to a method and apparatus for asynchronously transferring data from a first synchronous sequential logic circuit which derives its clock source from a first clock to a second synchronous sequential logic circuit which derives its clock source from a second clock, whereby metastability of the second synchronous sequential logic circuit is avoided. The invention comprises a data path and a control path; a data synchronizer coupled to the data path for synchronizing data signals; a control synchronizer coupled to the control path for synchronizing control signals; a register coupled in parallel to the data path for storing valid data output from the data synchronizer; a multiplexor having one input coupled to the data path, another input coupled to the register, a selector input coupled to the control path for selecting between receiving as input synchronized data signals or the contents of the register, and an output for transmitting valid data.

Abstract: A framed format identification signal is imbedded with a flagged format identification signal so that two terminals connected to a digital transmission network can automatically determine whether they are compatible and choose their preferred format for full communication.

Abstract: A data compression system can operate in a number of different configurations, and wherein the bit rate produced by a given configuration can be controlled over some finite range by a control signal from a rate controller for smoothly transitioning between the configurations so that discontinuous jumps in bit rate and distortion are minimized is provided by determining thresholds on the feedback control signals, the thresholds being used to determine when to switch in or out of each configuration; the thresholds furthermore being determined from the intersection points of the rate distortion curves for the available configurations.

Abstract: A delay stage for a ring oscillator supplies a first output signal and a second output signal. Each of the first and second output signals has a peak-to-peak voltage swing. The first and second output signals are complementary to each other. The delay stage includes a differential amplifier for generating the first output signal and the second output signal and a voltage clamping circuit for limiting the peak-to-peak voltage swing of the first and second output signals. The voltage clamping circuit is coupled between the first output signal and the second output signal. The differential amplifier includes a first NMOS transistor and a second NMOS transistor for generating the first and second output signals. The differential amplifier also includes a first PMOS transistor and a second PMOS transistor coupled to (1) the first and second NMOS transistors and (2) the voltage clamping circuit for providing bias currents to the first and second NMOS transistors.

Abstract: The apparatus and method describes herein shows a system of digitizing analog or digital electronic or optical signals with very high single bit serial digital data streams which digitizing is suitable to automatically adapt the transmission of multiple types of analog and digital signals. The system is especially well suited for allowing the coupling and transmission of signals.

Abstract: A transmission rate control system is adapted for an information processing system which exchanges data between a host unit and at least one terminal equipment via a first transmission line. The transmission rate control system includes a first part provided in the host unit for generating a clock switching signal which instructs a switching of a first clock signal which determines an operation of the terminal equipment, a second part provided in the terminal equipment for generating the first clock signal which determines the operation of the terminal equipment, a third part provided in the terminal equipment for switching a period of the first clock signal generated from the second part in response to the clock switching signal received from the main unit, so that a transmission rate of the terminal equipment is switched, and a second transmission line provided exclusively for transmitting the clock switching signal from the host unit to the terminal equipment.

Abstract: For quantization of subframe feature vectors representative of subframes identified by subframe indexes in each frame of a time sequential signal, such as an audio or a video signal, a first feature vector of a first subframe of a current frame is extracted with additional extraction of a second feature vector of a second subframe of the current frame and is quantized by a frame vector quantizer unit into a quantized frame vector for the current frame. Using a quantized frame vector for a previous frame and referring to interpolation coefficient vectors, an interpolator interpolates an interpolated feature vector for the current frame. An error vector is calculated between the interpolated and the second feature vectors and is quantized by an error vector quantizer unit into a quantized error vector. The subframe feature vectors are quantized by using the subframe indexes, the quantized frame vectors, the interpolated feature vector, and the quantized error vector.

Abstract: A roll off filter portion for an input transmission point signal executes a roll-off filtering process and an interpolation process with a multiple of two at the same time. The roll-off filtering process is adapted to form a frequency spectrum characteristic in a cosine roll-off shape for the input signal. An interpolator portion, connected to the roll-off filter portion, executes an interpolation process with a multiple of two. This process is a filtering process for forming a frequency spectrum characteristic in a cosine roll-off shape for an input signal. Depending on what multiple of the original sampling frequency a transmission point signal is interpolated, a corresponding number of the interpolator portions are connected in a cascade shape.

Abstract: A low complexity model based channel estimator is disclosed for use by a receiver in Rayleigh fading environments. The receiver contains at least one channel state estimator which uses an auto regressive model for channel variations. The channel state estimates are initialized by using at least preliminarily detected symbols. The receiver also contains a data detector which uses the received signal and the channel estimate, or a function thereof, delivered by at least one channel estimator to detect the transmitted symbols.

Abstract: In a variable modulation communication method, the transmission quality of a transmission path is monitored. If the transmission quality is good, communication is performed while the transmission time is shortened by using a multilevel modulation scheme. If the transmission quality is bad, communication is performed while the transmission time is prolonged by using a modulation scheme having a smaller number of levels than the multilevel modulation scheme. A variable modulation communication apparatus is also disclosed.

Abstract: A digital-transmission/analog-transmission changeover apparatus in a communication system for performing a digital transmission between a digital terminal and a terminal accommodated by an ISDN, and performing an analog transmission via the ISDN and an analog network, between the digital terminal and a terminal accommodated by the analog network includes a rate converter for converting the rate of data, which has entered from the digital terminal, to a rate suited to the ISDN, and for converting the rate of data, which has entered from the ISDN, to the rate of the digital terminal. A modulator/demodulator for modulating digital data, which has entered from the digital terminal, into an analog signal and demodulating the analog signal into digital data is provided. A PCM converter is connected to the modulator/demodulator for converting the analog signal into digital data at a rate suited to the ISDN, and converting digital data from the ISDN into the analog signal.

Abstract: A technique for reliable passage of handshaking information between a cellular modem and a land modem. Instead of bare transmission over a voice channel connection highly susceptible to signal fading and dropout, the initial modem handshaking exchange is instead FSK-encoded and broadcast using a network data signalling methodology already used to reliably pass signalling information between the base and registered mobiles. Automatic retransmission request signalling and transmission redundancy may be implemented to insure successful receipt at the receiving end of the radio link. Once received and verified, handshaking information is decoded and delivered to the destination modem in the appropriate format along cleaner fixed pathways. Reliable handshaking operations are contemplated whether the destination modem is a cellular modem registered in auto-answer mode (land-originated data call), or a land modem (mobile-originated data call).

Abstract: A system for determining the rate at which data has been encoded in the receiver of a variable-rate communications system. The data is received in frames having a fixed number of symbols. Multiple copies of symbols fill the frame when data is encoded at less than the full rate. At an encoding rate of one fourth the full rate, for example, each symbol in the frame is repeated four times. The incoming symbols are provided to multiple paths for decoding. Each path decodes the symbols at one of the possible rates. Error metrics, which describe the quality of the decoded symbols, are extracted and provided to a processor. The error metrics may include Cyclic Redundancy Check (CRC) results, Yamamoto Quality Metrics, and Symbol Error Rates. The processor analyzes the error metrics and determines the most probable rate at which the incoming symbols were encoded.

Abstract: A protocol for communication between devices connected via a bus having three handshake lines and at least one data line. A first device controls two of the three handshake lines, and a second device controls the third. The first device mixes toggling of the first and second handshake lines in a pattern which identifies a type of information packet. The second device polls the first and second handshake lines, and from the toggling pattern identifies the packet type. Once identified, the packet is transmitted according to a predefined format for the type. Typically, transmission of information is completed asynchronously using the handshake lines to carry request and acknowledge signals. In one embodiment, the protocol is implemented in a virtual reality system having a video game console as a first device and a head mounted display as the second device.

Abstract: A system for communicating signals within a digital network without the aid of an array of separate signal lines or of the system data bus. The network communication system 10 of the present invention is operative in accordance with a time-sliced protocol to communicate signal information among a set of digital modules 1. The communication system 10 includes a driver network for transmitting signal information to a first interface circuit 14 in communication with a first 22 of said modules during a selected interval of an interval cycle. The first interface circuit 14 includes an input network 44 for receiving the transmitted information during the selected interval. The inventive network communication system 10 further includes a kickstart circuit 30 for initiating an interval cycle upon the transmission of signal information within the network 10, or upon the execution of a maximum (Nth) interval of a preceding interval cycle.

Abstract: This disclosure describes an apparatus for data communication from a first data bus having a first clock frequency to a second data bus having a second clock frequency, asynchronous to the first frequency. The apparatus includes a synchronizer operative to sample data on said first data bus at a selected sampling rate and to provide such data to said second data bus at selected sampling rate.

Abstract: A selective call receiver (10) comprising a processor (108) that couples to a receiver circuit (102), a baud rate detector (106) and a memory device (110). The processor (108) activates the baud rate detector (106) that includes a plurality of registers to perform two baud rate detections to confirm a selective call signal before further processing. When a first baud rate detection detects the selective call signal, the processor (108) combines the results of this first baud rate detection and a plurality of predetermined baud rate parameters to provide a second plurality of predetermined baud rate parameters. The processor (108) then activates the baud rate detector (106) to perform a second baud rate detection using the second plurality of predetermined baud rate parameters. Based on the results of the second baud rate detection, the processor (108) determines whether to continue processing the selective call signal.

Abstract: A connecting apparatus for interconnection between serial data transmission devices, includes a DTE/DCE selector switch, a signal level converter, a single chip CMOS CPU and the RJ45 telephone bus cables, wherein the CPU controls the receiving and transmitting modes between the signal lines of the RS232 interface and the RJ45 telephone bus cables and also controls data transmission time so as to prevent the connected serial data transmission devices from sending out data at a time. The connecting apparatus can be connected with personal computers, serial printers, plotters or modems in series for data transmission to and from one another, and therefore jumper cables between either two data transmission devices are eliminated. Furthermore two connecting apparatus may be interconnected through RJ45 telephone bus cables, therefore it is easy to install and to expand data transmission devices.

Abstract: A system of distributing video and/or audio information employs digital signal processing to achieve high rates of data compression. The compressed and encoded audio and/or video information is sent over standard telephone, cable or satellite broadcast channels to a receiver specified by a subscriber of the service, preferably in less than real time, for later playback and optional recording on standard audio and/or video tape.

Abstract: An automatic modulation mode selecting unit (208) and a method (100) provide for selection from a plurality of modulation modes having an optimized transmission time for a data file. This is particularly useful where a small data file is to be transmitted, such as for a hand-held message pad. The present invention may select a modulation mode having a slow data rate but a short training time to achieve a shorter transmission time a small data file in comparison with using another modulation mode having a fast data rate but a longer training time, and thus a longer transmission time. The automatic modulation mode selecting unit includes a mode select controller (202), a mode computer (204), and a mode-select switch (206) for selecting a modulation mode based on a calculated optimized transmission time.

Abstract: A transceiver module for coupling between cells in a distributed intelligence network and a twisted pair line. The module receives power from the line and provides power to its respective cell. At the end of transmitting a packet, the transceiver transmits a code violation, then an anti-code violation to dissipate energy in the line. This is followed by clamping the line for the dead time between packets. N transceivers may be connected (without a cell) to form a repeater. The transceiver module may be used in a network having free topology; that is, an ideal transmission line, with terminators is not needed.

Abstract: An adaptive data rate modulator/demodulator (modem) (102), particularly useful for transmitting data over fading communications channels, uses an adaptive data rate technique which supports multiple data rates in the same device. The modem incorporates an adaptive data rate encoder (104) and an adaptive data rate decoder (105) using adaptive, parallel-branch decoding to translate received symbols into corresponding data bits. Significantly, the soft decision metrics of the decoder are also used to provide an estimate W of the signal-to-noise ratio. An optional predictor (232) receives W from the adaptive data rate decoder (105) and predicts the future signal-to-noise ratio to determine the desired data rate for the modem. The data rate is changed automatically and dynamically without interrupting the decoding process. A constant channel symbol rate and a single signal set simplify signal acquisition and synchronization.

Abstract: A data-transmitting apparatus contains first and second transmitters, a transmit transformer, and a connecting unit for coupling the transformer to an outgoing twisted-pair cable. The first transmitter filters data to produce outgoing data transmitted to the transformer at a first data rate. The second transmitter transmits outgoing data to the transformer at a different, typically greater, second data rate. A data-receiving apparatus contains first and second receivers, a receive transformer, and a connecting unit for coupling an incoming twisted-pair cable to the receive transformer. The first and second receivers receive incoming data from the secondary winding respectively at the first and second data rates. Incoming data is typically provided along data transfer paths that extend from the receive transformer in a daisy chain manner to the receivers. Data moving at either data rate can be transmitted and received without the need for hot switching in the data paths.

Abstract: A converter which is connected to a modulation/demodulation equipment having a first interface and to a terminal equipment having a second interface is disclosed. The converter includes a first connector for electrically connecting the converter to the modulation/demodulation equipment; a second connector for electrically connecting the converter to the terminal equipment; a signal converting circuit connected to the first connector and the second connector, for converting a signal input from the first connector into a signal which follows the second interface, the converted signal being output to the second connector, and for converting a signal input from the second connector into a signal which follows the first interface, the converted signal being output to the first connector; and a power supply circuit for supplying power to the modulation/demodulation equipment via the first connector.

Abstract: A methodology and concomitant circuitry for smoothing delay sensitive traffic utilizes short term traffic forecasts and guarantees meeting a prespecified delay constraint. The pattern of incoming traffic is used to forecast estimates of future incoming data from the present and past incoming data. Corresponding to the estimate is a data rate for propagating stored data to produce a smoothed outgoing data rate, and the interval of time over which such a rate is used so as to satisfy the delay constraint. The estimation procedure is then re-invoked at the end to the time interval, which takes into account data arriving during the time interval, so as to determine the next succeeding data rate and a new time interval for propagating stored data.

Abstract: A method and system are disclosed for permitting selected command sequences to be processed by a modem during data transfer operations. A preselected escape character is designated and inserted into a data stream to be applied to a modem in order to identify a selected command sequence which follows. A termination character is inserted into the data stream following the selected command sequence. Upon detection of the preselected escape character, the selected command sequence is coupled to a command processor within the modem and processed. In applications in which the modem is coupled between a data processing system and a cellular telephone communication channel, the selected command sequence may be utilized to transmit communication channel parameter status queries to a cellular telephone associated with the modem. In this manner, the Received Signal Strength Indicator (RSSI), bit error rate, or other indications of communication channel status may be queried.

Abstract: A method and system are disclosed for permitting selected command sequences to be processed by a modem during data transfer operations. A preselected escape character is designated and inserted into a data stream to be applied to a modem in order to identify a selected command sequence which follows. A termination character is inserted into the data stream following the selected command sequence. Upon detection of the preselected escape character, the selected command sequence is coupled to a command processor within the modem and processed. In applications in which the modem is coupled between a data processing system and a cellular telephone communication channel, the selected command sequence may be utilized to transmit communication channel parameter status queries to a cellular telephone associated with the modem. In this manner, the Received Signal Strength Indicator (RSSI), bit error rate, or other indications of communication channel status may be queried.

Abstract: A transmission system wherein the data transmission rate is optimized for communication between modems which are each capable of operating at various transmission rates and wherein the transmission medium is of variable quality. Prior to synchronization each modem determines an optimum transmission rate based on line quality, and during a synchronization setup phase the modems exchange information identifying their minimum and maximum acceptable transmission rates. An initial transmission rate is adopted and then adjusted up or down, depending on line quality, so that the rate is as close to the optimum rate as is consistent with line quality and the rates acceptable to both modems. Thus, the optimum rate calculated by each modem is taken into account and is imposed on the remote modem only if the latter is capable of operation at that rate. The system is therefore highly flexible and also reliable.

Abstract: This detector provides a computationally simple digital low power detector of symbol rate, also called baud rate. It uses an approximate Hilbert transform function to create approximate in-phase and quadrature signals. An approximate envelope detector (feature extractor) processes these signals to produce a signal with a strong frequency component at the symbol rate. This signal is then filtered, accumulated, and threshold detected. The approximate in-phase and quadrature signals are formed by a linear sequence of six delay elements, the output of the third delay element being the in-phase signal. A first summer receives the output of the second delay element at a minus input and the output of the fourth delay element at a plus input. A second summer receives the signal input at a minus input and the output of the sixth delay element at a plus input, and drives a right two bit shifter.

Abstract: A synchronization scheme for bidirectional data applications where the customer supplies data for transmission at a rate which is customer controlled. In accordance with the present invention, in each transmission direction, the customer data is converted into data symbols in a predetermined constellation. In response to these data symbols, additional symbols are added. In the disclosed embodiment, the additional symbols added are symbols lying outside of the constellation and are not used to represent customer data. The additional symbols added raise the symbol rate in each transmission direction to one higher than that provided by the symbols representative of the customer data alone. This higher symbol rate in each transmission direction is preferably the same, or the higher symbol rate in one direction is related to the higher symbol rate in the other direction by a rational number. At each receiver, the additional symbols are removed and customer data is recovered from its representative data symbols.

Abstract: A system and method for converting and combining multiple digital baseband signals into a composite IF signal for subsequent up converting and transmitting as an RF signal. The system and method use distributed symmetrical circuit architecture to form a composite IF signal from multiple identical converting elements which are daisy chained together to produce the composite signal from the converted signals in each element. Circuit complexity is reduced by the use of the multiple identical elements each of which may be readily formed from a standard integrated circuit.

Abstract: A repeater includes N repeater circuits coupled to integrator device in a star topology. Each of the N repeater circuits has an Input/Output port for transmitting a clock, data, control and collision signal. A request-for-access signal within the control signals is asserted as repeater circuit is requesting a data repetition. The integrator device has N Input/Output interfaces each of which is coupled to a corresponding Input/Output port, for selectively executing the data repetition and generating the collision signal, in response to the clock and control signals, so that the repeater functions as a single repeater.

Abstract: A calling station sends to a called station a call request package including the address of the called station and the information digitizing rate of the calling station. The packet may also include the address of the calling station. The called station selects the lower of the information digitizing rates of the calling and called stations or the information digitizing rates of both stations if such rates are the same. The called station sends to the calling station a call request response package including the selected information digitizing rate. The call request response packet may include the addresses of the calling and called stations. The calling station selects the lower of the information digitizing rates of the calling and called stations or the information digitizing rates of both stations if both rates are the same. The information digitizing rates of the calling and called stations may be the voice digitizing rates of both stations.

Abstract: Circuitry is described for providing a telephone line interface circuit of a MODEM for a computer with an AC impedance and DC voltage/current characteristics required by a given type telephone network such that the telephone line interface circuit can be matchingly connected with the given type telephone network. The given type telephone network provides an identification code representative of the required AC impedance and DC voltage/current characteristics. The circuitry comprises a plurality of impedance components that, when connected to the telephone line interface circuit, determine the AC impedance and DC voltage/current characteristics of the telephone line interface circuit. A plurality of terminals are coupled to receive a plurality of control signals associated with the identification code.