Abstract: Loop gain normalization is employed in adaptive filters to control weighting of the filter characteristic updates in order to converge properly to a desired filter characteristic. Filter instability is avoided during intervals that transient or other rapidly pulsating signals are received or inputted by normalizing the update gain with a representation of a so-called fast attack estimate of a prescribed characteristic of the input signal. In one embodiment the fast attack estimate is the maximum of a plurality of power estimates generated from a corresponding plurality of subsets of amplitude samples of the received signal. In another embodiment, the maximum of the magnitude representations of the input signal samples is modified to represent the fast attack power estimate of the received signal.

Abstract: In adaptive filters, under certain incoming signal conditions the tap coefficients tend to drift toward relatively large values. This condition has been countered by introducing so-called leakage into the tap coefficients which tends to drive them toward zero. Introduction of leakage is desirable under certain incoming signal conditions and not others. Indeed, during intervals that partial band energy, e.g., single frequency tones, multifrequency tones and the like, is incoming to the filter there is a need to introduce a relatively large leakage value into the tap coefficients. However, during intervals that whole band energy, e.g., speech or noise, is incoming to the filter no leak is desired or needed. This is realized by detecting intervals when partial band energy is incoming to the filter and controllably increasing the leakage value during those intervals.

Abstract: An ADPCM coder (100) converts a linear PCM input signal representative of PCM encoded speech or voiceband data into a quantized n-bit differential PCM output signal. Samples of the PCM input signal are delivered to a difference circuit (11) along with a signal estimate of the same derived from an adaptive predictor (12). The resultant difference signal is coupled to the input of a dynamic locking quantizer (DLQ). A quantized version of the difference signal is delivered from the output of said quantizer to an algebraic adder (17) where it is algebraically added with the signal estimate. The result of this addition is coupled to the input of the adaptive predictor, which in response thereto serves to generate the next signal estimate for comparison with next PCM sample. The adaptive quantizer has two speeds of adaptation, namely, a fast speed of adaptation when the input linear PCM signal represents speech and a very slow (almost constant) speed of adaptation for PCM encoded voiceband data or tone signals.

Abstract: Energy in a received signal is distinguished as being whole band energy or partial band energy by comparing an average value of the received signal to a modified magnitude value of the received signal. A signal representative of the comparison result is supplied to a filter including hysteresis for generating a signal to control representative of whether whole band or partial band energy is present. Hysteresis is provided in generation of the control signal by comparing the output amplitude of the filter to a first threshold value when the control signal is a first state and then comparing the filter output amplitude to a second lower threshold value when the control signal is a second state. When the modified magnitude value exceeds the average value, the received signal includes whole band energy, otherwise the received signal includes only partial band energy.

Abstract: Accurate and reliable measurements of transmission parameters, e.g., envelope delay distortion or frequency response, of a network or facility (105) are obtained in a test system (FIG. 1) employing digital data acquisition units (121) by utilizing a unique test signal including a plurality of tones. A set of test signals is transmitted over the facility (105), a set of measurements is made of the received version for each test signal, each set of measurements is time averaged, and an ensemble of time-averaged sets of measurements is used to generate the desired measurements of the transmission parameters. System efficiency is enhanced by measuring prescribed transmission impairments, e.g., nonlinear distortion (3OID), signal-to-noise ratio (S/N) and frequency shift (FS) on the facility under evaluation and dynamically determining test system parameters in accordance with predetermined relationships with the measured impairments (FIGS.

Abstract: Energy in a received signal is distinguished as being whole band energy or partial band energy by comparing an average value of the received signal to a modified magnitude value of the received signal. When the modified magnitude value exceeds the average value, the received signal includes whole band energy, otherwise the received signal includes only partial band energy.

Abstract: Errors in digital transmission are monitored by employing a cyclical-redundancy-check (CRC). A CRC code word having a predetermined number of bits is generated (via 310) from a block of bits (ESF) of a presently transmitted time division muliplexed (XTDM) signal. The code word bits are then inserted (via 304, 305, 306) into predetermined bit positions of the next subsequent block of bits (ESF) of the XTDM signal. In a receiver (FIG. 7), bits of a presently received time division multiplexed (RTDM) signal are compared (801, 802) to bits of a CRC code word generated from the last previously received block of bits to indicate errors in transmission. In a specific example, a 6-bit CRC code word is employed and the code word bits are inserted into predetermined framing bit positions.

Abstract: "Transhybrid" loss is maximized in a transmission network of the active canceler type employed to couple receive and transmit unidirectional transmission paths to a bidirectional transmission path including 2-wire loaded type cable by controllably adjusting impedance elements of the canceler circuit in a prescribed sequence including adjustment of a network build out capacitor to obtain amplitude nulls of signals detected on the transmit path while supplying individual ones of a plurality of test signals to the receive path. The test signals include first and second signals having a plurality of equally spaced frequency components in first and second frequency bands, respectively, and a third signal having a predetermined single frequency.

Abstract: A bidirectional transmission path is typically coupled to unidirectional receive and transmit paths to effect amplification in repeaters or the like. A determination of whether the bidirectional path includes either loaded or nonloaded type 2-wire cable is made by inserting a test signal having a predetermined frequency and a predetermined amplitude into the receive path and measuring the peak amplitude of a transmit signal developed on the transmit path. If the transmit signal peak amplitude is greater than a predetermined threshold value, the 2-wire cable is considered loaded type, and if the transmit signal peak amplitude is less than the threshold value, the 2-wire cable is considered nonloaded type.

Abstract: "Transhybrid" loss is maximized in a transmission network of the active canceler type employed to couple receive and transmit unidirectional transmission paths to a bidirectional transmission path including 2-wire nonloaded type cable by controllably adjusting impedance elements of the canceler circuit in a prescribed sequence to obtain amplitude nulls of signals detected on the transmit path while supplying individual ones of a plurality of single frequency test signals to the receive path. The adjustment sequence comprises a first procedure including a plurality of iterative adjustments of predetermined impedance elements in predetermined groups until no changes in the impedance settings occur and multiple iterative adjustment of predetermined groups until no changes in the impedance settings occur.

Abstract: Multifrequency (FIGS. 2 and 4) signals are generated by employing a microcomputer system (500) in conjunction with a digital-to-analog converter (506) and filter (507). Digital representations of amplitude values of the signals to be generated are stored in a read only memory (ROM 503) and sampled at a predetermined rate under control of a central processor unit (CPU 502) to generate digital signals representative of the desired multifrequency signal. The sampling rate is selected to be less than the theoretical Nyquist rate for the highest frequency tone in the multifrequency signal to turn to account the resulting so-called "alias" signals for generating tones closely spaced in frequency. In a specific example, the sampling rate is equal to twice the average frequency of the tones in the desired multifrequency signal. Unwanted harmonic components (3.omega..sub.0, etc.

Abstract: A smooth pulse sequence (SSM) which is a rational fraction (M/N) of an available uniform sequence (SIN) is generated by employing an address generator (10) and a read only memory (ROM 15). Signal representations are stored in the ROM (15) which define the smooth sequence pulse transitions. The address generator (10) is driven by the reference signal and, in turn, generates a sequence of address signals which, when applied to the ROM (15) cause the smooth pulse sequence (SSM) to be read out. The smooth pulse sequence (SSM) is filtered (16) and shaped (17) to obtain a desired uniform pulse sequence (SOUT) which is in synchronism with the reference signal (SIN).

Abstract: Manual mounting of large high density lead insertion connectors (1) onto circuit boards (3) is achieved by simultaneously engaging all connector leads (2) with a comb (9), sliding the engaged leads into alignment with receiving passageways (4) in the circuit board and pressing the connector leads into the receiving passageways. The comb has an exterior surface forming channels (10) corresponding in spatial relationship to the lead receiving passageways. A connector lead insertion apparatus (5, 6, 7, 8, 9, 10) is utilized in conjunction with the lead insertion method to hold the circuit board and connector in fixed position with respect to each other. The apparatus further permits the comb to be guided into proper position prior to engaging the connector leads.

Abstract: Framing of a digital receiver to synchronize with a true framing pattern is realized by employing an autonomous clock to generate framing pattern bits and other timing signal, and by employing a cyclical-redundancy-check (CRC) to eliminate the possibility of framing on false framing patterns. To this end, a frame synchronization circuit detects all possible framing candidate bit positions in a received time division signal and generates a frame resynchronization pulse corresponding to the framing candidate bit positions thereby causing the autonomous clock to synchronize to the associated framing pattern. If the framing pattern on which the clock is synchronized is a false one a loss of CRC signal is generated which initiates synchronizing on the next detected framing pattern. This process is iterated until no loss of CRC signal is generated thereby indicating synchronization on the true framing pattern.

Abstract: Accurate and reliable measurement results are obtained in a test system (FIG. 1) employing digital data acquisition units (121) when measuring frequency response or envelope delay distortion of a network or communication facility (105) by employing a unique test signal (21-tone) including a plurality of tones, each tone having amplitude, frequency, phase component values determined and assigned in accordance with prescribed criteria. The phase component values are determined in accordance with a relationship dependent on the number of tones in the test signal, and in one example, are initially assigned on a random, one-to-one basis to the tones. In a specific embodiment, a test signal is utilized having 21 tones. Further problems arising from nonlinearities on the facility under evaluation (105) are minimized by transmitting the 21-tone test signal a plurality of times and by reassigning the phase component values to the tones each time the test signal is transmitted.

Abstract: First-come, first-served bus allocation apparatus are distributed to each device sharing a common resource, such as a data bus. Bus allocation is achieved by placing each request from a device for control of the resource in an ordinal ranking with respect to requests from other devices. Requests are assigned positions in the ordinal ranking concurrent with other activity on the data bus. Substantially simultaneous requests are ordered sequentially. As control of the data bus is relinquished by one device, control is transferred to the device whose position in the ordinal ranking is contiguous with that of the relinquishing device. Delay in making this transfer is substantially eliminated.

Abstract: Transhybrid loss is maximized in a transmission network (FIG. 1, 101) of the type for coupling a bidirectional transmission facility (102, 2-wire) to receive (103) and transmit (104) unidirectional transmission facilities (4-wire) by automatically adjusting impedance elements (RKN, RZN, etc.) of an impedance network (202, FIG. 3, FIG. 4) to obtain an optimum match to the impedance of the bidirectional facility (102). To this end, individual ones of a plurality of tones (107) are supplied to a receive port (111) of the transmission network (101) and the impedance elements (RKN, RZN, etc.) are controllably adjusted in a prescribed sequence (FIGS. 8-16) to obtain amplitude nulls at a transmit port (112) of the transmission network (101). In one embodiment, predetermined ones of the impedance adjustments (RKN, RZN, etc., 820-823, 828-831) are iterated with predetermined ones of the tone signals being supplied to the receive port (111) further to optimize the impedance match.

Abstract: Transhybrid loss is maximized in a transmission network (FIG. 1, 101) of the type for coupling a bidirectional transmission facility (102, 2-wire) to receive (103) and transmit (104) unidirectional transmission facilities (4-wire) by automatically adjusting impedance elements (RKL and RZL) of an impedance network (202, FIG. 3) to obtain an optimum match to the impedance of the bidirectional facility (102). To this end, a plurality of tones (107) are individually supplied to a receive port (111) of the transmission network (101) and the impedance elements (RKL and RZL) are controllably adjusted in a prescribed sequence (FIGS. 7-10) to obtain amplitude nulls at a transmit port (112) of the transmission network (101). Then, an additional signal having a plurality of predetermined frequency components which repeat periodically is supplied to the receive port (111) and a predetermined one of the impedance elements (RKL) is again adjusted to obtain an average value amplitude null at the transmit port (112).

Abstract: Errors in test results are minimized in a test system (FIG. 1) employing digital data acquisition units (121) when measuring intermodulation distortion of a voice frequency communication facility (105) by employing a unique 3-tone test signal. To this end, the three tones have predetermined amplitude, frequency and phase relationships to obtain a test signal having a desired optimum probability density function which is substantially Gaussian. Additionally, circuit noise components are eliminated from the test results by obtaining a measure of noise with a single tone test signal and subtracting it out from the three tone test results. In a specific embodiment, a measure of the power spectrum resulting from the three tone signal and the power spectrum of the single tone signal are obtained, combined and utilized to obtain measurements of second and third order intermodulation distortion products compensated for noise.

Abstract: Compensation for errors in an amplitude conversion system caused by inaccuracies in and nonlinearities of system circuit components is realized by employing a self-compensation process in an amplitude measurement system (FIG. 1). In one embodiment first and second reference signals (from 111) are controllably supplied (under control of 105 via A1, A2SW1, SW2, 108, 112, 113 and 103) to a RMS-LOG converter circuit (104) to obtain a measure of the amplitudes of the reference signals (TA, TB) and convert the amplitudes into pulse signals. The pulse signals are supplied to a control circuit (105) for conversion into digital form and storage as reference numbers for future use. A test signal supplied from a remote location over a facility under evaluation is supplied (via T, R, 101, 102, 103) to the RMS-LOG converter (104) where the test signal amplitude (TMEAS) is measured and converted into a pulse signal.