# Recirculation correlator of resolution of phase-code manipulated signals

FIELD: radio engineering, possible use in radiolocation stations for allowing phase-code manipulated signals with approximately equal frequencies.

SUBSTANCE: input signal of device is an additive mixture of video-frequency phase-code manipulated signals with varying amplitudes and delays, encoded by M-series, digitized with temp in two counts on elementary analog quantization step in strobe M=4·n-1. By means of first adder and first shift register input signal by its recirculation amounts to interval, equal to 2·n. By means of first commutator signal is divided on even and odd series, which in turns pass to block of cross connections, then to block of fast Walsh transformation, and further to block of reverse check connections and second commutator. From the latter signals are sent to block for synchronization with elementary quantization step two counts long. Further signals are sent to third commutator, which in accordance to its evenness and oddness order sends them to second adder. By means of second adder and second shift register, signal from third commutator by its recirculation amounts to interval, equal to 2·n.

EFFECT: substantially decreased computer power costs due to recirculation transformation of input signals, making it possible to apply fast Walsh transformation.

3 cl, 8 cl

The invention relates to electrical engineering and can be used in radar stations to resolve visokomolekulyarnih (FCM) signals with approximately equal frequency.

Known correlator resolution of signals in time delay that contains one United block fast Fourier transform (FFT), the multiplier (functionally - divisor), the block of the inverse fast Fourier transform (OBPF), and the input device is the input of the FFT block, to the second input of the multiplier signal, having a structure of a diagonal matrix whose elements are the inverse of the discrete spectrum of the reference oscillation, the output device is output block OBPF [1].

However, the known correlator resolution has a relatively large computational cost due to the multiplier (functionally - divider) multi-digit numbers and two corresponding FFT.

The aim of the invention is the simplification of the circuit of the correlator resolution of signals in time delay, leading to a significant reduction of the computational cost due to the recirculation of conversion of input signals in order to apply the fast Walsh transform (MCR).

Figure 1 shows the structural diagram of the proposed recirculation correlator permission; figure 2 - structural diagram BL is 8 ka coordination with the elementary increments in the duration of two reference; figure 3 - building M-circulant and its conversion to semielemental M-sequence with the purpose of explanation building block 4 cross-connections and block 6 reverse cross-links; figure 4 is a plot illustrating the recirculation correlator permissions for the case of processing two FCM signals encoded semielemental M-sequence (n=7), discretized with a rate of two samples on a basic analog discretes (k=2) and delayed relative to each other six times in the gate of the N=2·n·k-1=27 times.

The device comprises a first adder 1, the first shift register 2, the first switch 3, block 4 cross-connections, unit 5 MCR, block 6 reverse cross-links, the second switch 7, block 8 coordination with elementary discrete duration in two counts, the third switch 9, the second adder 10, the second register 11 shift (figure 1).

Unit 8 coordination with elementary discrete duration in two reference contains the first and second registers 12 of the shift, the first and second registers 13 shifts by one count, the first and second adders 14 (figure 2.).

The first adder 1 contains two inputs and one output, the first input is the input device, the second input is connected to the last output of the first shift register 2, the output connected to the input of the first register 2 offset.

The first shift register 2 which contains one input, 2·n outputs, 2·n r-bit cells (r - the number depending on the bitness of the ADC), the outputs connected to respective inputs of the first switch 3.

The first switch 3 is designed for separation of output values of the first shift register 2 and contains 2·n inputs and n outputs, the outputs connected to respective inputs of block 4 cross-connections.

Block 4 contains cross-links n inputs and n outputs, the outputs connected to respective inputs of unit 5 MCR, and regard themselves must be constructed so that during the mixing of the input FCM signal, the encoded M-sequence carried out by the procedure of recycling, gate 4·n-1 to interval 2·n, the output values of the block of cross-connections coincided with one of the matrix rows of the Walsh-Hadamard transform (without the first row and first column): for example, for semielemental M-sequence 1110100, forming the polynomial x^{3}+x+1, is constructed M-circulant so that the first line of the M-circulant contained the original M-sequence, and subsequent lines were built by the cyclic shift by one element to the right (Fig 3, a). Next numbered columns of the received M-circulant from left to right (figa bottom row). Then the first l rows, where l=3 - degree generating polynomial of the M-sequence, and the selected value is I in the columns are translated into the decimal system,
considering the upper value of the low discharge (figa top row). These numbers will determine crosstalk, that is, the first input of the cross-ties will be connected to the first output of this block, the second with the sixth, the third with the second, fourth to seventh, fifth, fifth, sixth, fourth, and seventh to the third.

Unit 5 MCR contains n inputs and n outputs, the outputs connected to respective inputs of block 6 reverse cross-links. Fast Walsh transform is based on the well-known factorization algorithm hood [2]:

where Y_{n+1}- vector of size n+1 that represents the data after conversion;

matrix cofactors, composed of l components;

E_{2}elementary matrix of the Walsh function of size two by two;

I_{2}is the identity matrix of size two by two;

⊗ is the Kronecker symbol works;

X_{n+1}- vector of size n+1 that represent the original data.

Unit 5 MCR is designed to compute the vector Y_{n}that does not use the first row and first column of the matrix of Walsh-Hadamard transform.

Unit 6 reverse cross-links contains n inputs and n outputs, the outputs connected to respective input the AMI of the second switch 7, and they relationships are defined by the rule: the columns of the matrix (figa) are assigned sequence numbers (figa top row), then these columns are built in ascending order of their numbers; numbered rows and records the values of the elements of the matrix in the signal, that is, zero is equivalent to "+", and the unit is equivalent to "-" (figb). Now, if in the present example, the third and fourth lines are interchanged, and instead of the fifth row to put the seventh, sixth, fifth, seventh, sixth, add the top row and left column of zeros, then we obtain a canonical matrix of Walsh-Hadamard transform of size eight by eight (pigv). These changes will make the building of cross-connections, that is, the first input unit 5 reverse cross-links will be connected to the first output of this block, the second with the second, the third with the fourth, the fourth to the third, fifth to seventh, sixth, fifth, and seventh - sixth.

The second switch 7 includes n inputs and two outputs, the outputs connected to respective inputs of the block 8 coordination with elementary discrete duration two count.

Unit 8 coordination with elementary discrete duration in two reference contains two inputs and two outputs, the outputs of the block are connected to the corresponding inputs of the third switch 9.

The third switch 9 contains on the and of the inputs and one output, the output is connected to the first input of the second adder 10.

The second adder 10 has two inputs and one output, the second input is connected to the last output of the second register 11 of the shift, the output connected to the input of the second register 11 shift.

Second register shift has one input, 2·n outputs and 2·n cells corresponding to the bit, the outputs of the second register 11 shift are the outputs of the device.

The elements included in the block 8 coordination with elementary discrete duration in two countdown, connected in the following order: first and second registers 12 shift this block contains one input and one output, n r-bit cells, the input registers are input block, the output of the first shift register 12 is connected to the input of the first register 13 shift by one sample and with the input of the second adder 14, and the output of the second shift register 12 is connected to the input of the second register 13 shifts by one count and to the input of the first adder 14; first and second registers 13 shift one sample contains one input, one output and one r-bit cell, the output of the first register 13 shift by one sample is connected to the input of the first adder 14, the output of the second register 13 shift by one sample is connected to the input of the second adder 14; first and second adders 14 contain two inputs and one output, the outputs of the adders 14 you are what od unit 8 coordination with elementary discrete duration two count.

The proposed device is considered for the case of processing additive mixture of two videocasting FCM signals encoded semielemental M-sequence-1-1-11-111, discretized with a rate of two samples on a basic analog discretes k=2, different amplitude and delayed relative to each other on six counts, n=7, gate M=2·n·k-1=27 (figa). In the initial state in the cells of the registers 2, 12, 13, 11 shift recorded zeros.

The input of the first adder 1 receive timing input signal and being summarized in the course zero value of the last cell of the first shift register 2 is fed to the input of the first register 2 shift. The summation of the zero value of the last cell of the first shift register 2 in the first adder 1 is up until the first shift register 2 is written first fourteen values of samples of the input signal. Following the beat of the reference value in the last cell of the first register 2 offset added in the first adder 1 from the fifteenth to the value of the reference input signal and is recorded in the first cell of the first register 2 shift. Thus, the entire input signal is placed in the first register 2 shift (figb). After that, the recorded values in the first register 2 shift from the first to the fourteenth cell, proceed to the appropriate inputs of the first switch 3 is de first input unit 4 cross-connections are transmitted values of the odd-numbered cells of the first register 2 shift.
With outputs of block 4 cross-links these values to arrive at unit 5 MCR, where it calculates the vector Y_{7}for this sequence.

The output signal of unit 5 MCR is supplied to corresponding inputs of a block 6 reverse cross-links and then to the second switch 7 through the first output alternately placed in the first register 12 shift unit 8 coordination with elementary discrete duration two count. Then the first switch 3 takes values of even-numbered cells of the first register 2 shift, passes them to the appropriate inputs of the unit 4 is a cross-ties. With outputs of block 4 cross-links these values to arrive at unit 5 MCR, where it calculates the vector Y_{7}for this sequence. The output signal of unit 5 MCR is supplied to corresponding inputs of a block 6 reverse cross-links and then to the second switch 7 through the second output alternately placed in the second register 12 shift unit 8 coordination with elementary discrete duration two count.

In block 8 of the agreement with the elementary increments in the duration of two reference signals from the outputs of the first and second registers 12 shift in the order of his odd and parity in turn fed to the input of the first and second register 13 shifts by one count, respectively, where delayed by one sample, and the first inputs Vtorov the first and adders 14, respectively, where are summed with the corresponding delayed data samples. At this time, the third switch 9 in the order of odd parity and parity in turn relieves the values obtained from outputs of the first and second adders 14 block 8 coordination with the elementary increments in the duration of two frames and transmits them to the first input of the second adder 10, where, being summarized in the course of the last value of the second register 11 shift, arrive at the input of the second register 11 shift.

The output signal of the device is removed from the outputs of the second register 11 shift. The peculiarity of the output signal of the device is single level and uniform nature of the correlation noise (pigv).

Analysis of the known and proposed device shows that for the calculation of the two FFT in the known device requires 2·n·log_{2}n operations of multiplication of complex numbers and n multiplication (divisions) in the multiplier (functionally - divider), and in the proposed device, due to the MCR, you want to calculate n·log_{2}n algebraic operations on complex numbers of typethereby significantly increasing the performance of the proposed device.

Literature

1. V.k.sloka, Geekaren. Algorithms of signals in digital processing. - M.: the USSR Academy of Sciences, RTI, Preprint 848, 1984

2. Amirhan, Whatman fundamentals of theory of discrete signals on finite intervals. - M.: Owls. radio, 1975.

1. Recirculation correlator resolution visokomolekulyarnih (FCM) signal contains the first and the second adder, the first and second shift registers, the first, second and third switches, the unit of cross-connections, the unit is fast Walsh transform, block reverse cross-links, the block matching with elementary discrete duration two count, and the input device is a first input of the first adder, and the output device are the outputs of the second shift register, the second input of the first adder is connected to the last output of the first shift register, the output of the first adder connected to the input of the first shift register, 2·n outputs which is connected to the corresponding inputs of the first switch, the n outputs of which are connected to the corresponding inputs of the block cross-links, n outputs which are connected to the corresponding inputs of the block fast Walsh transform, n outputs which are connected to the corresponding inputs of the block reverse cross-links, n outputs which are connected to the corresponding inputs of the second switch, the two outputs of which are connected to corresponding inputs of block coordination with elementary discrete duration in two counts, two outputs which are connected to the corresponding inputs of the third to the mutator, which in turn is connected to the first input of the second adder, the output of which is connected to the input of the second shift register, the last output of the second shift register connected to the second input of the second adder.

2. Recirculation of the correlator according to claim 1, characterized in that the block matching with the elementary increments in the duration of two reference contains the first and second shift registers, inputs of which are the inputs of the specified block, the first and second shift registers one count, the first and second adders, the outputs of which are outputs of the specified block, the output of the first shift register connected to the input of the first shift register by one count and the first input of the second adder and the output of the second shift register connected to the input of the second shift register by one count and the first input of the first adder, the outputs of the first and second shift registers for one countdown respectively connected with the second inputs of the first and second adders.

3. Recirculation of the correlator according to claim 1, characterized in that it comprises a unit cross-links, which contains cross-links, which should be constructed so that during the mixing of the input FCM signal, the encoded M-sequence carried out by the procedure of recycling, gate 4·n-1 times in the interval 2· n times, the output values of the block of cross-connections coincided with one of the matrix rows of the Walsh-Hadamard transform, which is the first row and the first column.

**Same patents:**

FIELD: modulation and demodulation in reception and transmission including when using expanded signal spectrum.

SUBSTANCE: proposed method for digital communications with signal whose spectrum is expanded by modulation using complementary Golay numbers involves following procedures: during transmission input binary data are integrated into η groups of m = log_{2}A bits, A modulation by peak values, spectrum expansion by means of η complementary Golay numbers or by complementary Golay numbers whose phase and sign are changed, modulation in N-phase keying mode, and transmission over communication channel; reception involves phase demodulation, convolution with respective Golay complementary numbers, amplitude demodulation, and source data generation.

EFFECT: enhanced transfer speed and spectrum expansion ratio.

7 cl, 4 dwg

FIELD: technology for recognizing radio-signals, in particular, methods for detecting type and modulation parameters of radio signals.

SUBSTANCE: for realization of method during recognition received radio signal is digitized by time and quantized by level. Value of bearing and clock frequencies of signal are determined and cophased and quadrature components of radio signal are formed. These are then filtered and selection counts of cophased and quadrature components of radio signal are selected, taken in counting time moments, determined by value of clock frequency. After that, selection counts of cophased and quadrature components of radio signal are corrected in complex form, using gradient algorithm for adjusting corrector coefficients. Then estimate of selections is split onto given number of clusters, equal to position coefficient of recognized signals, and values of clusterization error functional are calculated, received values are compared and decision is taken about relation to class by minimum of error functional value.

EFFECT: increased probability of correct recognition under multi-beam conditions.

5 cl, 9 dwg

FIELD: radio engineering.

SUBSTANCE: known digital device for demodulation of discontinuous signals in multi-beam communication channel, having block for transformation of input signal, solving circuit, shift register and demodulation block, consisting of N serially connected detection blocks and N-input adder, additionally has (M-1) demodulation blocks and M-input adder, and in each of N blocks for detecting each of M demodulation blocks, additionally inserted are power measuring device and device for forming weight coefficient.

EFFECT: higher resistance of receipt to interference and compatibility of device with multi-position signals receipt.

1 dwg

FIELD: radio engineering.

SUBSTANCE: device, having bearing oscillation generator, output of which is connected to signal input of first key and to input of first phase shifter, output of which is connected to signal input of second key, outputs of first and second keys are connected to appropriate inputs of adder, output of which through multiplier is connected to output of device, device additionally has pseudo-random series generator, clock input of which is connected to output of clock pulse generator, and synchronization input is connected to output of synchronization pulse generator and to second synchronization means input, first input of which is input of information signal, and output is connected to second multiplier input, device also includes commutation block, M decoders, M-2 keys, M-2 phase shifters, pseudo-random series delays block.

EFFECT: better concealment and detection protection level of generated signal.

6 dwg

FIELD: radio engineering.

SUBSTANCE: device implements algorithms of discontinuous Fourier transformation and fast folding of received and bearing signals, to provide search-less detection of complicated signals with sizeable bases. Digital synchronized filter processes at video-frequency with use of standard digital assemblies and elements. Device has multipliers 3,4,14,15, phase changer 2 for π/2, circuit for delay for length of signal element 1, low frequency filters 5,6, analog-digital converters 7,8,12, microprocessor systems of discontinuous Fourier transformation 9,10, microprocessor systems of reversed discontinuous Fourier transformation 16,17, generator of bearing pseudo-random series 11, microprocessor systems of discontinuous Fourier transformation of bearing pseudo-random series 13, square-ware generators 18,19, adder 20, arithmetic device for taking square root 21, threshold device 22, discontinuous process pulse generator 23, device for splitting frequency in two 24, clock generator 25, interconnected by appropriate functional connections.

EFFECT: broader functional capabilities, higher efficiency.

2 dwg

FIELD: radio engineering, applicable in antiference radiolinks.

SUBSTANCE: the method is featured by the fact that the pseudorandom sequence with clock pulse f_{p} and for expansion of the spectrum is divided into two orthogonal sequences, one of which contains only even harmonics of the initial pseudorandom sequence, and the other - only the odd ones, then each of the obtained sequence is multiplied with a simple phase-manipulated signal, then the upper side band is separated from the spectrum of one obtained signal, and the lower side band - from the spectrum of the other signal, these unlike side bands are summed up, in each side band two narrow sections of the spectrum symmetrical relative to frequency f_{0}+1/2f_{p}, in the upper side band and relative to frequency f_{0}-1/2f_{p} in the lower side band, one of the separated sections of the spectrum in each side band of the separated spectrum sections is amplified to the known magnitude, and the other, symmetrical to it, is inverted, after which the separated and remained non-separated sections of the spectrum in both side bands are summed up, the separated narrow spectrum sections in each side band are altered according to the pseudorandom law.

EFFECT: enhanced anti-interference of the radiolink is attained due to the fact that in the method of normalization of the composite phase-manipulated signal consists in expansion of the spectrum of the simple phase-manipulated signal obtained by multiplication of the carrying sinusoidal oscillation with frequency f_{0} and the binary information signal.

6 dwg

**FIELD: radio engineering; portable composite phase-keyed signal receivers.**

**SUBSTANCE: proposed receiver has multiplier 4, band filter 6, demodulator 8, weighting coefficient unit 5, adding unit 7, analyzing and control unit 10, synchronizing unit 3, n pseudorandom sequence generators 2 ^{1 }through 2^{n}, decoder 1, and switch unit 9. Receiver also has narrow-band noise suppression unit made in the form of transversal filter. Novelty is that this unit is transferred to correlator reference signal channel, reference signal being stationary periodic signal acting in absence of noise and having unmodulated harmonic components that can be rejected by filters of simpler design than those used for rejecting frequency band of input signal and noise mixture. Group of synchronized pseudorandom sequence generators used instead of delay line does not need in-service tuning.**

**EFFECT: facilitated realization of narrow-band noise suppression unit; simplified design of rejection filters.**

**1 cl, 8 dwg**

**FIELD: automatic data acquisition systems. **

**SUBSTANCE: proposed method designed for data acquisition from burglar and fire alarm sensors, electricity, heat, and gas meters, and from fiscal memory of cash registers involves use of unique random or pseudorandom plurality of differences in initial phases of closest harmonic pairs, mentioned plurality being chosen so as to minimize peak factor of total signal. In case of operation of fire alarm sensor it is sufficient to transfer only one character to alarm control console unambiguously identifying location of operating sensor; as a rule, such character is conditional number or address pre-assigned to sensor.**

**EFFECT: reduced power requirement of subordinate system units and/or enhanced range of their operation.**

**1 cl, 2 dwg**

FIELD: communications engineering, in particular, technology for transferring service in mobile communications system and for identification of boundary of cell for transferring equipment between various mobile communication systems.

SUBSTANCE: mobile terminal identifies boundary of mobile communication system cell, supporting asynchronous system, for transferring service between various communication systems. For this, base boundary setting station determines anew the code words for denoting boundary, different from existing code words, utilized for reaching frame synchronization, and transfers one of code words for denoting boundary in each frame along secondary synchronization channel. When receiving code word for denoting boundary along secondary synchronization channel, mobile terminal recognizes, that it is positioned at the limit of mobile communication network, supporting asynchronous system, and performs transfer of service to mobile communication network, supporting synchronization scheme.

EFFECT: possible identification and differentiation of cell boundaries.

4 cl, 5 dwg

FIELD: communications engineering.

SUBSTANCE: at transmitting side additionally provided is channels activity analyzer and additional generators of orthogonal signals for dividing active channels, and at receiving side - additional blocks for processing orthogonal signals for dividing active channels and analyzer of signals for dividing active channels, and also transfer of information messages about increments of substantial computations with utilization of additional orthogonal signals for dividing active channels.

EFFECT: increased informational capacity of system by increasing capacity of multi-channel route, increased serviced sources of information.

3 dwg

FIELD: measurement technology; measuring signal-to-noise ratio.

SUBSTANCE: proposed method involves measurement of single-channel signal noise power by means of single-channel demodulator of multichannel receiving device on receiving end. Total noise power is found by equipartial addition with measured noise power of each single-channel signal. Signal power S is found by measuring after combination of maximal ratio of each single-channel signal. Signal-to-noise ratio of signal obtained is found by dividing signal power by total noise power. Device implementing this method has noise power meter in RAKE adder and signal power meter past RAKE adder.

EFFECT: enhanced noise measurement efficiency affording great amount of data enabling real-time response to changes in channel characteristics.

8 cl, 4 dwg, 1 tbl

FIELD: engineering of communication systems.

SUBSTANCE: communication system has transmitter, meant for transformation of serial data stream to parallel data and for segmentation of parallel data on multiple blocks, having multiple data blocks; for inserting supporting data, having information, representing value of phase or position, where supporting symbol is inserted, into each segmented sub-block; reversed fast Fourier transformation of responsible block into time signals, wherein frequencies of sub-bearing lines are separately assigned to data blocks; and determining phase multipliers of reversed fast Fourier transformation subjected time signals for decreasing ratio of peak power value to average power value, where nonlinear distortion occurs due to match of phases between reversed fast Fourier transformation subjected data blocks and sub-bearing frequencies; and rotation of phase of reversed fast Fourier transformation subjected signals in accordance to determined phase multipliers prior to actual transmission.

EFFECT: decreased ratio of peak power value to average power value.

6 cl, 12 dwg

FIELD: wireless duplex communications.

SUBSTANCE: sub-channels are set for physical random access channel in wireless duplex communication with temporal channels separation, in which multiple access is used with code separation of channels. Sub-channels transfer information between system users and system network. A row of radio channel frames has series of temporal ranges. For certain number of temporal row in a series each sub-channel of certain number of temporal range is uniquely set by one frame of radio channel from aforementioned row.

EFFECT: simplified network-level interface.

3 cl, 5 dwg

FIELD: mobile telecommunication systems.

SUBSTANCE: base station receives information, pointing out presence on mobile station of information for transfer. Then, base station transmits information about state of use of physical channels and information about maximal allowed possible data transfer speed. Mobile station receives aforementioned data and transmits access header to base station to request given physical channel, determined on basis of aforementioned data.

EFFECT: higher stability, decreased number of errors during assignment of channel.

3 cl, 52 dwg, 8 tbl

FIELD: communication systems.

SUBSTANCE: method includes forming paging channel message combined with Walsh series with length not less than 2m, which is then sent at data transfer speed below 480 bits per second. By transmitting message of paging channel at low data transfer speed and integration of gathered energy message can penetrate into buildings and other structures or environments with high level of fading.

EFFECT: higher efficiency.

4 cl, 6 dwg

FIELD: transmission of information, applicable in cellular and satellite communication systems.

SUBSTANCE: the receiver has two frequency converters, two quadrature correlators, phase error filter, controlled oscillator, two control elements, error delay filter, controlled clock oscillator, reference signal generator, two multipliers, two analog-to-digital converter, delay line, demodulator, decoder, two matched filters, phase shifter.

EFFECT: enhanced power efficiency of the communication system.

2 cl, 3 dwg

FIELD: communications engineering.

SUBSTANCE: proposed band selection method for mobile orthogonal frequency division multiple access communication system includes following steps to classify procedures of band selection between sending end and receiving ends with respect to original band selection process, passband width selection process, and periodic band selection process: determination of source band selection code (SC)number for source band selection process; SC number to request passband width for passband width request selection process and periodic SC number for periodic band selection process; determination of periodic SC deferment value in compliance with periodic SC number, and transmission of source SCs, passband width request SC, periodic SCs, and periodic SC deferment values on receiving ends.

EFFECT: minimized time for band selection access.

22 cl, 3 dwg, 4 tbl

FIELD: radio engineering.

SUBSTANCE: implementation of soft decisions generating method in case of receiving multi-beam signal allows substantial decrease of complication level of receiver, because it contains lesser amount of one-beam receivers, than a prototype.

EFFECT: increased interference resistance and increased capacity of communications system during receiving of multiple-beam signal due to efficient periodic procedure of renewal of multiple-beam signal components when receiving estimates of components search, also considering mutual influence of signal components.

6 cl, 13 dwg

FIELD: radio engineering.

SUBSTANCE: suggested algorithm for quasi-coherent receipt of multi-beam signal with continuous pilot signal is based on algorithm, adaptive to freeze frequencies, for estimation of complex skirting curve, which uses both pilot and information signal. Use of information symbols for estimation of complex skirting curve allows, with weak pilot signal, to substantially increase precision of estimation of said curve and, as a result, significantly decrease possible error of information parameters estimation.

EFFECT: higher interference resistance.

2 cl, 10 dwg