Abstract: A method for transmitting messages is described which is based on the idea of using bit groups of a data packet, which are not required for assigning the bit groups to a specific logic channel, for transmitting a type of information specific to the bit group for the purpose of transmitting a different type of information. In particular new signaling information, the importance of which could not yet have been recognized when the data packets or the bit group structure thereof was being defined, or the transmission of which was not yet regarded as necessary when laying down the transmission standard.

Abstract: A method is disclosed for generating a PCM code set for encoding data by a PCM encoder in a data transmission system having a digital modem with a PCM encoder, a digital signal transmission path, an analogue signal transmission path with a central office line interface portion, and an analogue modem. The method includes the step of determining a minimum signal level distance between adjacent PCM codes of the PCM code set, the minimum signal level distance enabling discrimination by the analogue modem. Then a line interface attenuation of the central office line interface portion is determined. Finally, the PCM code set on the basis of a power limit computed by adding the line interface attenuation to a central office line interface power limit is generated. The invention further relates to an analogue modem to be operated in such a data transmission system.

Abstract: A method for determining the encoding law of an incoming signal in a network which possibly contains an A-&mgr; or &mgr;-A conversion includes obtaining digital impairment learning (DIL) probing data, generating an ordered table of levels therefrom, using the table to find two functions, and using a logical analysis of the functions to determine the encoding law of the signal. A first function is a maximum from the values DL(i) and the threshold Th1 which are less than T(i), with T(i)=a+bi, and DL(i)=L(i+16)−2L(i) with L(i) being the DIL signal corresponding to the transmitted Ucode=i.

Abstract: Method and apparatus for transmitting encoded signals with increased data speed in communications system using system clock synchronization and bit robbing techniques to attain high transmission rates is provided.

Abstract: A data stream between transcoders of a mobile wireless system is subdivided into a first data stream with samples for transmission and a second data stream with signal parameters for reconstruction of user data and/or for signaling. Both data streams are transmitted at the same time permitting an improvement in the quality of transmitted data, e.g. speech data in a GSM network in tandem operation between mobile subscribers.

Abstract: A method and device for combating logarithmic quantization and Robbed Bit Signaling (RBS) impairments that..are typical to PCM telephone lines is descried. An apparatus is described which includes a front-end unit which receives samples of the digital PCM line, an impairment identifier unit which identifies samples that have a high likelihood to have, large impairments due to the PCM line, an impairment estimator unit which estimates the value of impairment caused by the digital line, a samples reconstructor unit which fixes received samples by subtracting from them the value of the estimated impairment and an output unit transfers the reconstructed samples to a receiver. The method allows improving signal quality at the output of the PCM line, and thus improving data rates and robustness of digital communication receivers, and particularly of V.34 receivers, or V.90 transceivers that are digitally linked to the PCM, line.

Abstract: The receiver of a PCM modem utilizes the V.90 TRN1d training signal for detecting whether any of the six slots of the received signal may be subject to alternating robbed bit signaling (ARBS), and what the alternating robbed bit signaling pattern may be. This is accomplished by accumulating the received level over a plurality of frames for each slot and by comparing the received levels for each slot to an average level for that slot. If the difference between the received levels and the average levels exceeds a threshold, the slot is determined to be subject to ARBS. Where a slot is subject to ARBS, DIL sequence signals for frames of the alternating robbed bit signaling slot having LSB=0 and LSB=1 are accumulated separately (if available) in order to generate two translation tables (TRT0, TRT1) for that slot. Where the DIL sequence is found only in the frames having the alternating robbed bit signaling slot having LSB=0 or having LSB=1, only one translation table can be generated.

Abstract: Hardware and resource usage penalties associated with the conventional remote device management approach of occupying a robbed DS0 channel for only one management session at a time are obviated by programming a multi-digital circuit servicing host site-resident integrated access device to provide for effective simultaneous management of multiple remote digital communication devices by one or more workstations. Although only a single robbed in-band (T1) channel per remote site is used, it is unnecessary to terminate each high speed digital (T1) link with an associated T1 Service Unit and ISDN Service Unit pair at the central office site.

Abstract: The currently defined industry standard framing structure for 2B1Q ISDN signaling, at 160 kilobaud, provides 128 kbps for a customer (B1, B2) data channel, and 16 kbps for a data (D) channel. Of the remaining 16 kbps non payload bandwidth, 4 kbps are used for overhead maintenance data. Eight kbps of the remaining 12 kbps of non payload bandwidth, that customarily transport a repeated framing pattern, are usurped for the transport of an auxiliary compressed (from 64 KHz to 8 KHz) digitized voice POTS channel, that is sufficient to transport toll quality voice. The remaining framing pattern bandwidth is adequate prevent an unacceptable reduction in bit error rate.

Abstract: Short pseudo-random (PR) probing sequences that comply with ITU V.90 digital impairment learning (DIL) descriptors provide DIL probing sequences that yield high performance in severe inter-symbol interference (ISI) channels. The short PR sequences do not require the insertion of extra zero symbols to get rid of ISI. Further, a novel receiving structure corrects for propagation of digital impairment common in conventional equalizers for an ISI free receipt of the probing sequences within the strictly time constrained probing sequence. Based on the reliably received signals, general digital impairment mapping tables, digital pads, regular and strange RBS patterns, and different types of PCM codecs (A-law/&mgr;-law) are identified.

Abstract: A method for training a receiving modem connected through a telephone network to correct for differences between a transmitted and a received symbol occasioned by network impairments including robbed bit signaling which preempts a least significant bit of a customer's data depending on the frame assigned by the network for such connection.

Abstract: A method and apparatus for detecting the location of robbed bits by a digital communications network. A complete echo cancellation circuit also is disclosed employing the robbed bit detection method and apparatus in which the coefficients of the echo cancellation FIR filter are trained simultaneously during the detection of the position of the robbed bit or bits.

Abstract: A signalling method in a wireless digital telecommunication system, where the signals between a base station and a terminal comprise bursts generated from symbols. The symbols comprise at least one stealing symbol indicating, if necessary, the use of a traffic channel for signalling. The symbols are generated from several bits by modulating and the stealing symbol is used for transmitting various signalling messages. A signalling message to be transferred is coded into a code word which is placed into one or more stealing symbols. The code word may be interleaved into the stealing symbols of several bursts. The method can be used, for example, for controlling the transmission power of the mobile station and the base station.

Abstract: A signalling method in a wireless digital telecommunication system, where the signals between a base station and a terminal comprise bursts generated from symbols. The symbols comprise at least one stealing symbol indicating, if necessary, the use of a traffic channel for signalling. The symbols are generated from several bits by modulating and the stealing symbol is used for transmitting various signalling messages. A signalling message to be transferred is coded into a code word which is placed into one or more stealing symbols. The code word may be interleaved into the stealing symbols of several bursts. The method can be used, for example, for controlling the transmission power of the mobile station and the base station.

Abstract: A universal DS-0 channelized format is provided wherein selected states of CAS bits are used to indicate to the transport mechanism when DS-0 channels are not being used for voice and are available for use for data transport. In addition, the T1 frame format carries CAS bits only in the first DS-0 channel, so that robbed bits are disabled and not used to carry ABCD signaling bits, thereby avoiding any risk of data corruption. Still further, a special CAS signaling value not defined as a CAS state, is employed in a frame nibble instead of a frame counter to indicate that the state is in the first DS-0 slot.

Abstract: This invention enables various types of equipment using different protocols to be multiplexed on to a two-wire line carrying traffic with a predetermined protocol. Transmissions from equipment which uses separate information and signalling channels are multiplexed on to a single channel of the predetermined protocol with the signalling incorporated in to the channel by the use of bit-robbing techniques.

Abstract: The invention is an ATM system to route DS0 traffic from T1 Extended Superframe (ESF)or Superframe (SF) systems that use robbed bit signaling. The invention is able to route the call selecting the ATM VPI/VCI that routes the call within the ATM system. DS0s with robbed bit signaling are transported transparently by the ATM system.

Abstract: System and method for controlling a telecommunications device such as an echo canceller within a telecommunications system. The system and method include and involve a switching system that is configured to receive a call from a calling station and to route said call within said telecommunications system, and an ancillary telecommunications device that is configured to control a call processing parameter to affect said call. The switching system and the ancillary telecommunications device are coupled to each other via a channelized call data network. The channelized call data network is configured to communicate data corresponding to the call over at least one data channel. The ancillary telecommunications device may control the call processing parameter to affect the call based on a directive issued by the switching system to the ancillary telecommunications device during the call. The directive is contained within at least one channel of the channelized call data network.

Abstract: In a communications arrangement, a first pulse code modulation (PCM) modem communicates data in the form of PCM words with a second PCM modem through a public switched telephone network (PSTN). The transmitted signal representing the data may be affected by type A and/or type B robbed bit signaling occasioned by the PSTN such that the least significant bits (LSBs) of certain PCM words are “robbed” and substituted with signaling bits. In addition, the transmitted signal is attenuated because of a digital loss imposed by a switch in the PSTN. During training of a PCM modem, any occurrence of type A and/or type B robbed bit signaling is identified, and a signal level conversion table in accordance with the invention is created. Based on this table which takes into account the digital loss, the most likely transmitted PCM word is determined, given a received signal level.

Abstract: In a communications arrangement, a first pulse code modulation (PCM) modem communicates data in the form of PCM words with a second PCM modem through a public switched telephone network (PSTN). Transmitted signals representing PCM words may be affected by robbed bit signaling occasioned by the PSTN such that the least significant bits (LSBs) of certain transmitted PCM words are “robbed” and substituted with signaling bits. In addition, the transmitted signals are attenuated because of a digital loss imposed by a switch in the PSTN. During training of a PCM modem, any occurrence of robbed bit signaling is identified, and a signal level conversion table is created. This table contains each transmitted PCM word and the received signal level corresponding thereto. In accordance with the invention, the digital loss is measured based on those received signal levels in the table which are free of robbed bit signaling.

Abstract: A signalling method in a wireless digital telecommunication system, where the signals between a base station and a terminal comprise bursts generated from symbols. The symbols comprise at least one stealing symbol indicating, if necessary, the use of a traffic channel for signalling. The symbols are generated from several bits by modulating and the stealing symbol is used for transmitting various signalling messages. A signalling message to be transferred is coded into a code word which is placed into one or more stealing symbols. The code word may be interleaved into the stealing symbols of several bursts. The method can be used, for example, for controlling the transmission power of the mobile station and the base station.

Abstract: In a communications arrangement, a first pulse code modulation (PCM) modem communicates data in the form of PCM words with a second PCM modem through a public switched telephone network (PSTN). The transmitted data may be affected by type A and/or type B robbed bit signaling occasioned by the PSTN such that the least significant bits (LSBs) of certain PCM words are “robbed” and substituted with signaling bits. Any such type A and/or type B robbed bit signaling is detected using two different training sequences during training of the second PCM modem. The would-be PCM words affected by either robbed bit signaling are identified to the first PCM modem. The latter then avoids transmitting data using the LSBs of those PCM words. In addition, through the training, a decision feed-back equalizer in the second PCM modem is properly adjusted, taking into account any robbed bit signaling affecting the transmitted training data.

Abstract: Detection and compensation for periodic disturbances in sampled data such as the error introduced by robbed bit signaling (RBS) in a digital carrier system. A period of N samples, e.g., six or twelve frames, at which the periodic disturbance repeats is identified for collecting a subset of the sampled data, i.e., samples taken from a common frame. In a digital telephone network (DTN), the RBS disturbance repeats at an integer multiple of 6 frames; signaling bits A, B in a superframe (SF), or at a period of 12 frames. In an extended superframe (ESF), the RBS may repeat every 24 frames, using signaling bits A, B, C, D in one of every sixth frame. An embodiment detects the presence of the periodic robbed bit signaling disturbances in sampled data by integrating the least significant bits (lsbs) of the subset samples from a frame to determine whether in-band signaling is being performed in the frame.

Abstract: A device and method for detecting digital impairments affecting an upstream pulse code modulation (PCM) channel in a digital communication network, involves; receiving, by a digital PCM modem interconnected to the digital communication network, a random sequence of digital values selected from a constellation of digital values transmitted over the upstream PCM channel of the digital communication network; establishing distributions of the received digital values, each distribution corresponding to one of a plurality of time intervals; and deriving from the distributions the types of robbed bit signaling and digital loss affecting the upstream PCM channel of the digital communication network for each time interval.

Abstract: Methods are provided for generating at least one translation table for a modem having a frame having a plurality of slots. DIL sequence information from another modem is used to generate ordered table of levels, and distances between adjacent levels of the ordered table for found for each slot. The distances are used to distinguish between slots subject to robbed bit signaling (RBS) and slots not subject to RBS, and the ordered tables are used to make a determination as to whether the DIL sequence information is A-law or &mgr;-law information. Scaling factors are generated from the A-law/&mgr;-law determination as well as from a PAD estimation, and the scaling factors are utilized in generating translation tables. A PAD estimation function is utilized in finding the PAD estimation.

Abstract: A method in a modem having a frame having a plurality of slots, for determining whether incoming DIL sequence information contains A-law or &mgr;-law information is provided. From the DIL sequence information, an ordered table of levels for each slot is generated. The levels of all non-robbed-bit slots are averaged, and average levels are subjected to an A-law/&mgr;-law separation function.

Abstract: A method, apparatus and article of manufacture are described. In particular two network interface devices that are connected over a path that includes a digital trunk using robbed-bit signaling use a technique to identify the presence of robbed-bit signaling. The network interface devices synchronize to bytes that are subject to robbed-bit signaling. The network interface devices must synchronize to the robbed-bit signaling to avoid transmitting information or receiving information in these signaling positions. The network interface devices then take advantage of the least significant bit positions of frames that are not used for robbed-bit signaling. This results in an increase in data carrying capacity from 56 kps to 62.7 kps.

Abstract: The invention is an ATM system to route DS0 traffic from T1 Extended Superframe (ESF) or Superframne (SF) systems that use robbed bit signaling. The invention is able to route the call selecting the ATM VPI/VCI that routes the call within the ATM system. DS0s with robbed bit signaling are transported transparently by the ATM system.

Abstract: The present invention provides a method for conveying information over a communication network such as a Digital Loop Carrier network free of in-band signaling information for at least a portion of an established communication between at least two users so as to reduce the information error rate associated with the established communication.

Abstract: A method of detecting the presence of signal impairments that introduce distortion in one or more time slots of a communication link by comparing a received training sequence of signal points with hypothetical received signal points, where the hypothetical points are predistorted versions of the training sequence, and are based on the known, predetermined training sequence of signal points. A detection matrix is formed where one dimension of the matrix corresponds to a time slot within a frame, preferably six time slots to a frame, and the other dimension corresponds to a particular impairment, or combination of impairments. The individual signal impairments are generally one or more of the following: robbed bit signaling where the robbed bit is replaced with a logic `0`; robbed bit signaling where the robbed bit is replaced with a logic `1`; robbed bit signaling where the robbed bit is replaced with a logic `1/2`; 3 dB digital attenuator; 6 dB digital attenuator.

Abstract: A device system and method of detecting impairments in a communication network, involving: receiving during a plurality of time intervals equalized training signals which are produced from training symbols that have been transmitted over the network and equalized; generating reference symbols corresponding to the training symbols and equalized training signals; indexing the equalized training signals by their time intervals and corresponding reference symbols; calculating errors due to impairments from the indexed, equalized training signals; and detecting impairments in the network from the calculated impairment errors.

Abstract: A method, apparatus and article of manufacture are described. In particular two network interface devices that are connected over apath that includes a digital trunk using robbed-bit signaling use a technique to identify the presence of robbed-bit signaling. The network interface devices synchronize to bytes that are subject to robbed-bit signaling. The network interface devices must synchronize to the robbed-bit signaling to avoid transmitting information or receiving information in these signaling positions. The network interface devices then take advantage of the least significant bit positions of frames that are not used for robbed-bit signaling. This results in an increase in data carrying capacity from 56 kps to 62.7 kps.

Abstract: A pulse code modulation modem system is configured to transmit data from a first modem to a second modem over the public switched telephone network (PSTN). The PSTN employs robbed bit signaling (RBS) such that symbols affected by RBS arrive at the second modem in a periodic manner based on a period of six symbols. The modem system is configured such that signal segments are formatted and transmitted with six symbols per segment. After obtaining symbol synchronization, the second modem initializes a modulo-6 symbol counter such that the zero count corresponds to the first symbol of each received signal segment. Those symbols affected by RBS are identified and analyzed to determine optimized signal point constellations that may be used to compensate for the RBS on a symbol-by-symbol basis during subsequent encoding and decoding. Upon a loss of synchronization, the second modem resets its modulo-6 counter in response to the detection of the first symbol in a subsequent signal segment.

Abstract: A noncooperative feedback system is provided for a compensation system associated with, for example, a transmitter or codec, for enabling the compensation system to improve the accuracy of digital signals transmitted to a, digital network. The noncooperative feedback system is particularly suited for providing feedback to a compensation system for correcting distortion resulting from rob bit signaling (RBS), digital loss, or other types of digital signal degradation. The noncooperative feedback system includes a compensation selector in a transmitter (e.g., digital modem, analog modem, codec, etc.) that combines different compensations with frames of digital data by way of an addition mechanism to produce modified digital data frames. The transmitter is configured to transmit the modified digital data frames into the digital network. A receiver (e.g., digital modem, analog modem, etc.

Abstract: The object of the invention is a method to realize discontinuous transmission (DTX) in a telecommunications network, e.g. in a GSM (Global System for Mobile Communications) mobile phone network, particularly on the downlink. The disadvantage of known methods is that dummy bursts transmitted on the frequency of the broadcasting channel cause disturbing responses in a mobile phone, when frequency hopping is used. In the solution according to the invention the bursts transmitted on the frequency of the broadcasting channel are encoded so that after decoding the mobile phone prevents information contained in a dummy burst to be interpreted as speech. In this way the mobile phone responds with noise on the dummy bursts transmitted on the broadcasting frequency.

Abstract: A method and system for transmitting control information, such as Fast Associated Control Channel (FACCH) information in a digital TDMA communication system. Control information, when required, is transmitted over every other TDMA frame, and speech and data are transmitted over the remaining TDMA frames. Coding protection is reduced during transmission of the control information.

Abstract: A pulse code modulation modem system is configured to transmit data from a first modem to a second modem over the public switched telephone network (PSTN). The PSTN employs robbed bit signaling (RBS) such that symbols affected by RBS arrive at the second modem in a periodic manner based on a period of six symbols. The modem system is configured such that signal segments are formatted and transmitted with six symbols per segment. After obtaining symbol synchronization, the second modem initializes a modulo-6 symbol counter such that the zero count corresponds to the first symbol of each received signal segment. Those symbols affected by RBS are identified and analyzed to determine optimized signal point constellations that may be used to compensate for the RBS on a symbol-by-symbol basis during subsequent encoding and decoding. Upon a loss of synchronization, the second modem resets its modulo-6 counter in response to the detection of the first symbol in a subsequent signal segment.

Abstract: The invention is a method for transporting a voice band signal with channel-associated signaling over an ATM system. The method comprises converting the signal into ATM cells so that the sequence numbers in the cells correspond to the location of the signaling in the cells. After transmission over the ATM system, the ATM cells are converted back into the signal using the sequence numbers in the cells to locate the signaling in the cells. The convergence sublayer indication bit of a segmentation and reassembly protocol data unit header of an ATM adaption layer 1 ATM cell can be used as a portion of the sequence numbers so that the sequence numbers can use a repeating 12-count sequence.

Abstract: A method and apparatus for demodulating includes differential-detecting an input signal into which a unique word is inserted, correlating an output of the differential-detection and a data table obtained by differential-detecting the unique word, detecting a time when an electric power of a correlation output which exceeds a threshold value becomes the local maximum, reading the input signal stored in a buffer from the leading end of the unique word, estimating a frequency error of the input signal based on a phase of the correlation output, obtaining a signal by removing the frequency error from the read signal and inverse-modulating a unique word portion in the signal in which the frequency error has been removed, according to a data of a unique word table, and then reproducing a carrier signal.

Abstract: A communications device is presented that allows dynamic bandwidth allocation of an unswitched data path based upon the current utilization of one or more switched data channels. The device operates over the local loop of a digital communications carrier, such as a T1 line, that has a variety of time division multiplexed channels. Each data channel can be configured to operate as a channel dedicated to carrying unswitched data on the unswitched data path, or as a switched channel. Switched channels maintain status information about their current status, allowing switched data communication when the channel's status is active, and permitting the unswitched data path to utilize the channel when the channel's status is idle. In one embodiment, channel status information is passed to a remote unit by altering a redundant robbed-bit signaling bit in a multiframe. In a second embodiment, channel status is determined by monitoring switching information that is already transmitted about the channel.

Abstract: A method for reducing signal degradation in a Digital Loop Carrier System by removing signaling information normally embedded continuously in digital information being conveyed over the system. The system remains in this signaling free communication mode until it detects a change in its supervisory condition requiring that it exit from the signaling free communication mode or terminate communication allowing the system to enter an idle mode.

Abstract: A rob bit compensation system improves the accuracy of digital signals received from and transmitted to a digital network, such as a telephone network, that employs rob bit signaling (RBS) wherein the network periodically robs a bit for its own use. The system can be employed within a digital modem or a coder/decoder (codec), each of which is interconnected with the digital network that periodically robs a bit every nth frame, where n is, for example, 6 or 24. The system can be implemented in association with the receive subsystem of the digital modem or in the communications paths within the codec associated with receiving data from the digital network. The system includes a compensation control utilized to detect when a least significant bit (LSB) of a particular frame of data consistently exhibits a certain logic state, either a mark (logical 1) or a space (logical 0). When an LSB of a particular frame does consistently exhibit the certain logic state, then the particular frame is considered an RBS frame.

Abstract: A method of communication between a master unit and a slave unit, including the steps of: sending at least a command byte from the master unit to the slave unit including data byte counter bits to be interpreted by the slave unit according to the following rule set; if said data byte counter bits belong to a first set, then said data byte counter bits contain information representing a number of associated data bytes, which is the expected number of data bytes; if said data byte counter bits belong to a second set, then said data byte counter bits contain information representing a number which must be decoded before the expected number of data bytes is obtained; receiving at least the command byte; interpreting the command byte; and receiving the number of data bytes required by the rule set.

Abstract: Controlled activation of a message-waiting light of a telephone unit of a PBX system, that is coupled over a two-wire link to a foreign exchange subscriber circuit terminating a digital communication link, is carried out by hardware and software modifications to each of FXO and FXS channel units at opposite ends of the digital communication link. These modifications are effective to rob redundant signalling bits of extended superframe format time division multiplexed digital communication signals to transport a prescribed request code, that instructs the FXS circuit to generate a message-waiting light driving signal on the tip-ring pair to the message-waiting phone.

Abstract: A method of and system for monitoring the conditions of channels in a multichannel telecommunications line, wherein each of the traffic channels uses A/B bit signaling to signal their condition. Whenever the system detects a setup acknowledgment message in a command channel that includes a call reference and a channel identifier, the system displays the detected setup acknowledgment message and monitors the channel identified by said channel identifier for a change in line status, as indicated by a change in its A/B bits. In response to detection of a change in the A/B bits of the channel identified by the channel identifier, the system decodes the A/B bits and displays the changed line status.

Abstract: A cooperative feedback system is provided for a compensation system associated with, for example, a transmitter or codes, for enabling the compensation system to improve the accuracy of digital signals transmitted to a digital network. The cooperative feedback system is particularly suited for providing feedback to a compensation system for correcting distortion resulting from rob bit signaling (RBS), digital loss, or other types of digital signal degradation. The cooperative feedback system includes a compensation selector in a transmitter (e.g., digital modem, analog modem, codec, etc.) that combines compensations with frames of digital data by way of an addition mechanism to produce modified digital data frames. The transmitter is configured to transmit the modified digital data frames into the digital network. A receiver (e.g., digital modem, analog modem, etc.

Abstract: A telecommunications system and method for minimizing interruptions to voice transmissions due to the transmission of overriding control signals is disclosed. Since FACCH and other control signals replace or block-out speech data, the quality of speech transmissions deteriorates the longer the control transmission. Through modifications to the FACCH protocol, lengthy sequential FACCH or other control transmissions are divided into a plurality of discrete control segments, which are transmitted non-sequentially throughout a speech transmission, and queued at the receiving end. After receipt of all of the control segments, the original control message is reconstructed and forwarded for processing.

Abstract: A method of detecting the presence of robbed-bit signaling within the digital portion of a telephone network. A communication system includes an encoder and a decoder. The encoder has a digital connection to the digital portion of the telephone network. The digital portion of the telephone network is connected by an analog loop to the decoder. The method includes sending a predetermined pattern of PCM codewords from the encoder, through the telephone network, to the decoder. An error measurement is taken at the decoder. The presence of robbed-bit signaling is determined based upon the error measurement.

Abstract: A two-level or three-level probing signal is generated by a transmitter for transmission over a channel and for detection and analysis by a receiver. The two-level probing signal is a signal having a first PCM .mu.-law level over a first frame, and a second PCM .mu.-law level over a second frame. The two-level probing signal when combined with detection and analysis is generally sufficient for determining the presence and order of RB-signaling and PAD attenuation, and the extent of PAD attenuation may also be determined. The three-level probing signal is similar to the two-level probing signal but includes a third .mu.-law level over a third frame. A preferred two-level probing signal is a signal having a PCM .mu.-law level of .+-.975 for a first frame, and a signal having a PCM .mu.-law level of .+-.1023 for a second frame (or vice versa), although other sets of signals such as .+-.1087 and .+-.879 can be utilized. One preferred three-level probing signal is a signal having a PCM .mu.-law level of .+-.

Abstract: A compensation system is configured to improve the accuracy of digital signals that are communicated through a digital network by reducing loss from digital attenuation quantization (DAQ; digital pad quantization) and rob bit signaling (RBS). The combined DAQ/RBS compensation system can be employed within a transmitting modem connected to the digital network and is constructed as follows. In a first embodiment, a first adjustment mechanism combines a DAQ compensation quantity with each segment of the digital data, prior to transmission, in order to enhance accuracy of the received digital data. The value of the DAQ compensation quantity depends on feedback that is provided to the compensation system during a series of test transmissions.