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W-lvetica#|x`H1`D4PkC"S^11>bbu"::Dg1:11bbbbbbbbbb11gggbuuuk1Xubuukuuuk111Rb:bbXbb1bb''X'bbbb:X1bXXXX;.;g:=::m:::mmmmm::::::mm:k1mubububububXubububub11111111bbbbbbbbbuXubbkbuXmmmmumububXXXXbububububbmbbbbbb:k:k::=kmmX:uXb'b:b:b:b'bmbbbb:::uXuXuXuXk:k:k:mbbbmbuXkXkXKQmmmm^b:kbbbbmbA@mmbmmbmmmmmmm:b:mmmbbmmmmmmmmmmmmXXmmmmmmmmmmmmmmmmmmcm`m`mm`m:mmmmmm}}}mjjmmmmmmmmmmmmmmm0mm}mmmmmmmmmmmmmmmmmmmmmmm}Mmmmmmmmmmmmmjmmmtmmmmmmmmm`'mmm`mmjmlWmmmmmmmmmmmmmmmmmmmW`mmmmjmMQMS PS Jet Plus /800 II QPJPII.PRSPl`D4PkCg2W_qD|xHelveticaCourier@,`H1`D4PkCmQrrr r  @C2 KLTG@,`H1`D4PkCmQrrr r  @C;,>>> >  @C ` X` hp x (#%'HP    x|@  3'3'Standard6'6'StandardC6QMS $=R- Ot  ` `  <  <AP IX150E OOt#  ` `  <  <AP IX150E O9 (3303) a (3303)  X 13.2HRecommendation G.961 < DIGITAL TRANSMISSION SYSTEM ON METALLIC LOCAL <LINES FOR ISDN BASIC RATE ACCESS 1.HGeneral 1.1HScope  `  HThis Recommendation covers the characteristics and parameters of a digital transmission system at the network side of the NT1 to form part of the digital section for the ISDN basic rate access. HThe system will support the H full duplex;(# H bit sequence independent.(# Htransmission of two Bchannels and one Dchannel as defined in Recommendation I.412 and the supplementary functions of the digital section defined in Recommendation I.603 for operation and maintenance. HThe terminology used in this Recommendation is very specific and not contained in the relevant terminology Recommendations. Therefore Annex B to Recommendation G.960 provides a number of terms and definitions used in this Recommendation. 1.2HDefinition   HFigure 1/G.961 shows the boundaries of the digital transmission system in relation to the digital section. Note In this Recommendation digital transmission system refers to a line system using metallic lines. The use of one intermediate regenerator may be required.  FIGURE 1/G.961 ' Digital section and transmission system boundariesă  N*ԌHThe concept of the digital section is used in order to allow a functional and procedural description and a definition of the network requirements. Note that the reference points T and V1 are not identical and therefore the digital section is not symmetric. HThe concept of a digital transmission system is used in order to describe the characteristics of an implementation, using a specific medium, in support of the digital section. 1.3HObjectives HConsidering that the digital section between the local exchange and the customer is one key element of the successful introduction of ISDN into the network the following requirements for the specification have been taken into account. H to meet the error performance specified in Recommendation G.960;% H to operate on existing 2wire unloaded lines, open wires being excluded;% H the objective is to achieve 100% cable fill for ISDN basic access without pair selection, cable rearrangements or removal of bridged taps (BT) which exist in many networks;% H the objective to be able to extend ISDN basic access provided services to the majority of customers without the use of regenerators. In the remaining few cases special arrangements may be required;% H coexistence in the same cable unit with most of the existing services like telephony and voice band data transmission;% H various national regulations concerning EMI should be taken into account;% H power feeding from the network under normal or restricted conditions via the basic access shall be provided where the administration provides this facility;% H the capability to support maintenance functions shall be provided.% 1.4HHAbbreviations%H HA number of abbreviations are used in this Recommendation. Some of them are commonly used in the ISDN reference configuration while others are created only for this Recommendation. The last one is given in the following: HBER  Bit Error Ratio HBT  Bridged Tap HCISPR  Comit) International Sp)cial de Perturbation Radio)lectrique H (now part of IEC) HCL  Control Channel of the line system HECH  Echo Cancellation HEMI  ElectroMagnetic Interference N*Ԍ HDLL  Digital Local Line HDTS  Digital Transmission System HNEXT  NearEnd Crosstalk HPSL  Power Sum Loss HTCM  Time Compression Multiplex HUI  Unit Interval 2.HFunctions HFigure 2/G.961 shows the functions of the digital transmission system on metallic local lines. Note 1 The optional use of one regenerator must be foreseen. Note 2 This function is optional. '  FIGURE 2/G.961 ' Functions of the digital transmission systemă 2.1HBchannel HThis function provides, for each direction of transmission, two independent N* 64 kbit/s channels for use as Bchannels (as defined in Recommendation I.412). 2.2HDchannel HThis function provides, for each direction of transmission, one Dchannel at a bit rate of 16 kbit/s, (as defined in Recommendation I.412). 2.3HBit timing HThis function provides bit (signal element) timing to enable the receiving equipment to recover information from the aggregate bit stream. Bit timing for the direction NT1 to LT shall be derived from the clock received by the NT1 from the LT. 2.4HOctet timing HThis function provides 8 kHz octet timing for the Bchannels. It shall be derived from frame alignment. 2.5HFrame alignment HThis function enables the NT1 and the LT to recover the time division multiplexed channels. 2.6HActivation from LT or NT1 HThis function restores the Digital Transmission system (DTS) between the LT and NT1 to its normal operational status. Procedures required to implement this function are described in section 6 of this Recommendation. HActivation from the LT could apply to the DTS only or to the DTS plus the customer equipment. In case the customer equipment is not connected, the DTS can still be activated. Note The functions required for operations and maintenance of the NT1 and one regenerator (if required) and for some activation/deactivation procedures are combined in one transport capability to be transmitted along with the 2B + Dchannels. This transport capability is named the CLchannel. 2.7HDeactivation HThis function is specified in order to permit the NT1 and the regenerator (if it exists) to be placed in a low power consumption mode or to reduce intrasystem crosstalk to other systems. The procedures and exchange of information are described in section 6 of this Recommendation. This deactivation should be initiated only by the exchange (ET). See note in 2.6. 2.8HPower feeding HThis optional function provides for remote power feeding of one regenerator (if required) and NT1. The provision of wetting current is recommended.  (3303) : (3303)  h  X Note The provision of line feed power to the usernetwork interface, normal or restricted power feeding as defined in Recommendation I.430 is required by some administrations. 2.9HOperations and Maintenance HThis function provides the recommended actions and information described in + Recommendation I.603. HThe following categories of functions have been identified: H maintenance command (e.g., loopback control in the regenerator or the NT1);p& H maintenance information (e.g., line errors);p& H indication of fault conditions;p& H information regarding power feeding in NT1.p& HSee note in 2.6. 3.HTransmission medium 3.1HDescription HThe transmission medium over which the digital transmission system is expected to operate, is the local line distribution network. HA local line distribution network employs cables of pairs to provide services to customers. HIn a local line distribution network, customers are connected to the local exchange via local lines. HA metallic local line is expected to be able to simultaneously carry bidirectional digital transmission providing ISDN Basic Access between LT and NT1. HTo simplify the provision of ISDN basic access, a digital transmission system must be capable of satisfactory operation over the majority of metallic local lines without requirement of any special conditioning. Maximum penetration of metallic local lines is obtained by keeping ISDN requirements at a minimum. HIn the following, the term Digital Local Line (DLL) is used to describe a metallic local line that meets minimum ISDN requirements. 3.2HMinimum ISDN requirements Ha)  No loading coils; Hb)  No open wires; Hc)  When BTs are present, some restrictions may apply. Typical allowable HHX BT configurations are discussed in section 4.2.1.p&  h`  3.3HDLL physical characteristics  ` ( HIn addition to satisfying the minimum ISDN requirements, a DLL is typically constructed of one or more twistedpair segments that are  ( spliced together. In a typical local line distribution network, these twistedpair segments occur in different types of cables as described in Figure 3/G.961.  +Ԍ FIGURE 3/G.961 & DLL Physical modelă 3.4HDLL electrical characteristics 3.4.1HInsertion loss HThe DLL will have nonlinear loss versus frequency characteristic. For any DLL of a particular gauge mix, with no BTs and with an insertion loss of   X dB at 80 kHz, the typical behaviour of its insertion loss versus frequency is depicted in Figure 4/G.961. !FIGURE 4/G.961 (  Typical insertion loss characteristic without presence of BTs Note The maximum value of X ranges from 37 dB to 50 dB at 80 kHz. The minimum value could be close to zero. 3.4.2HGroup delay HTypical ranges of values of DLL group delay as a function of frequency are shown in Figure 5/G.961.  +Ԍ HHX X XP %P  `  <FIGURE 5/G.961 < <Typical group delay characteristică  ` ( Note The maximum value of one way group delay (T) ranges from 30 to 60 microseconds at 80 kHz. 3.4.3HCharacteristic impedance HTypical ranges of values of the real and imaginary parts of the characteristic impedance of twisted pairs in different types of cables are shown in Figure 6/G.961.  +Ԍ XFIGURE 6/G.961 X% XTypical ranges of values of real and imaginary ă Xparts of characteristic impedance 3.4.4HNearend crosstalk (NEXT)  (X HThe DLL will have finite crosstalk coupling loss to other pairs sharing the same cable. Worstcase NEXT Power Sum Loss (PSL) varies from 44 to 57 dB at 80 kHz (refer to section 4.2.2). HThe DLL loss and PSL ranges have been independently specified. However, it is not required that all points in both ranges be satisfied simultaneously. A combined DLL loss/PSL representation is shown in Figure 7/G.961 to define the + combined range of operation. !FIGURE 7/G.961 (  Combined representation of DLL loss/PSL range of operationă 3.4.5HUnbalance about earth HThe DLL will have finite balance about Earth. Unbalance about Earth is described in terms of longitudinal conversion loss. Worstcase values are shown in Figure 8/G.961.  + Ԍ !FIGURE 8/G.961 (  Worstcase longitudinal conversion loss versus frequencyă 3.4.6HImpulse Noise HThe DLL will have impulse noise resulting from other systems sharing the same cable as well as from other sources. 4.HSystem performance 4.1HPerformance requirements HPerformance limits for the digital section are specified in  4 of Recommendation G.960. The digital transmission system performance must be such that these performance limits are met. For that purpose, a digital @t2 %  #AP IX150E @?tt% %  #AP IX150E ?transmission system is required to pass specific laboratory performance tests that are defined in the next sections. 4.2 HPerformance measurements HLaboratory performance measurement of a particular digital transmission system requires the following preparations: Ha)  definition of a number of DLL models to represent physical and electrical characteristics encountered in local line distribution networks;ƀ% Hb)  simulation of the electrical environment caused by finite crosstalk coupling loss to other pairs in the same cable;ƀ%  N* ԌHc)  simulation of the electrical environment caused by impulse noise;ƀ% Hd)  specification of laboratory performance tests to verify that the performance limits referred to in section 4.1 will be met. ƀ% 4.2.1HDLL physical models HFor the purposes of laboratory testing of performance of a digital transmission system providing ISDN Basic Access, some models representative of DLLs to be encountered in a particular local line distribution network are required. The maximum loss in each model is optionally set between 37 and 50 dB at 80 kHz to satisfy requirements of the particular network. Similarly, the lengths of BTs are optionally set within the range defined in Figure 9/G.961.  + Ԍ !FIGURE 9/G.961 ( DLL physical models for laboratory testingă Note 1 The value of X varies from 37 to 50 dB at 80 kHz. Note 2 Equivalent gauges can be used. For example 0.6mm is equivalent to AWG 22. AWG stands for American Wire Gauge. 4.2.2HIntrasystem crosstalk modelling 4.2.2.1HDefinition of intrasystem crosstalk HCrosstalk noise in general results due to finite coupling loss between pairs sharing the same cable, especially those pairs that are physically adjacent. Finite coupling loss between pairs causes a vestige of the signal flowing on one DLL (disturber DLL) to be coupled into an adjacent DLL (disturbed DLL). This vestige is known as crosstalk noise. Nearend crosstalk (NEXT) is assumed to be the dominant type of crosstalk. Intrasystem NEXT or self NEXT results when all pairs interfering with each other in a cable carry the same digital transmission system. Intersystem NEXT results when pairs carrying different digital transmission systems interfere with each other. Definition of intersystem NEXT is not part of this Recommendation. HIntrasystem NEXT noise coupled into a disturbed DLL from a number of DLL disturbers is represented as being due to an equivalent single disturber DLL with a coupling loss versus frequency characteristic known as PSL. Worstcase PSL encountered in a local line distribution network is defined in Figure 10/G.961. All DLLs are assumed to have fixed resistance terminations of Ro Ohms. The range of Ro is 110 to 150 Ohms.  N* Ԍ !FIGURE 10.G.961 ( Worstcase Power Sum Loss (PSL)ă 4.2.2.2HMeasurement arrangement HSimulation of intrasystem NEXT noise is necessary for performance testing of digital transmission systems. Intrasystem noise coupled into the receiver of the disturbed DLL depends on: Ha)  Power spectrum of the transmitted digital signal. The power spectrum is a function of the line code and the transmit filter;ƀ% Hb)  Spectrum shaping due to the PSL characteristic of ƀ% HHX Figure 10/G.961.ƀ%  X`   `  HThe measurement arrangement of Figure 11/G.961 can be used for testing of performance with intrasystem crosstalk noise.  + Ԍ  FIGURE 11/G.961 ' Crosstalk Noise Simulation and Testingă HThe measurement arrangement in Figure 11/G.961 is described in the following: Ha)  box 1 represents a white noise source of constant spectral density. Spectrum is flat from 100 Hz to 500 kHz rolling off afterwards at a rate  20 dB/decade;% Hb)  box 2 is a variable attenuator;% Hc)  box 3 is a filter that shapes the power spectrum to correspond to a particular line code and a particular transmit filter;% Hd)  box 4 is a filter that shapes the power spectrum according to the PSL characteristic of Figure 10/G.961;% He)  box 5 is a noise insertion circuit which couples the simulated crosstalk noise into the DLL without disturbing its performance. The insertion circuit therefore must be of sufficiently high output impedance relative to the magnitude of the characteristic impedance of the DLL under test. A value  4.0 K2 in the frequency range 0 to 1 000 kHz is recommended.% HBoxes 3, 4 and 5 in Figure 11/G.961 are conceptual. Dependent on the particular realization, they could possibly be combined into one circuit. The measurement arrangement in Figure 11/G.961 is calibrated according to the following steps: Ha)  by terminating the output of Box 5 with a resistor of a value of Ro/2 Ohm, and measuring the true r.m.s. (rootmeansquare) voltage across it in a bandwidth extending from 100 Hz to over 500 kHz. The power dissipated in the Ro/2 resistor is 3 dB higher than the power coupled into the receiver of the DLL under test;% Hb)  the shape of the noise spectrum measured across the Ro/2 resistor should be within:% H  +1 dB for values within 0 dB to 10 dB down from the theoretical peak;%  N*Ԍ  HHX ©X +3 dB for values within 10 dB to 20 dB down from the theoretical peak;H!  `   ` 8 H for measurement purposes a resolution bandwidth of  10 kHz is recommended;Ơ# Hc)  the peak factor of the noise voltage across the Ro/2 resistor should be  4. This in turn fixes the dynamic range requirements of the circuits used in the measurement arrangement.Ơ# HWith the specified calibrated measurement arrangement, intraystem crosstalk noise due to a worstcase PSL can be injected into the DLL under test while monitoring its performance. The noise level can be increased or decreased to determine positive or negative performance margins. 4.2.3HImpulse noise modelling 4.2.3.1HDefinition of impulse noise HImpulse noise energy appears concentrated in random short time intervals during which it attains substantial levels. For the rest of the time impulse noise effects are negligible. 4.2.3.2HMeasurement arrangement HFigure 12/AB shows a possible arrangement for impulse noise testing. FIGURE 12/G.961 & Impulse Noise Simulation and Testingă HThe impulse noise source in Figure 12/G.961 is for further study. Two possible classes of impulse noise signals are described in the following: H white noise of flat spectral density level of 510 V/ Hz and a bandwidth > 4 times the Nyquist frequency of the particular system. The peak factor of the noise must be > 4;Ơ# +Ԍ H a particular waveform, as represented in Figure 13/G.961.Ơ# FIGURE 13/G.961 & Possible Waveform to Simulate Impulse Noiseă & Note In some local line distribution networks and as a national option, crosstalk noise performance tests are considered sufficient to evaluate a particular digital transmission system. In such cases proper DLL engineering rules are applied to guard against impulse noise. 4.2.4HPerformance tests  8X HFive types of tests are required to describe the overall performance of a particular digital transmission system to qualify it for operation over the local line distribution network modelled in this Recommendation. 4.2.4.1HDynamic range HDynamic range performance describes the ability of a particular digital transmission system to operate with received signals varying in level over a wide range. DLL models 1 and 2 in Figure 9/G.961 have a loss varying from very low (0 dB) to very high (37 50 dB at 80 kHz). HWhen testing with DLL models 1 and 2 in Figure 9/G.961, no errors should be observed in any 15 minutes (provisional) measuring interval when monitoring any Bchannel. HSpecification of data sequences to be used for this measurement are for further study. 4.2.4.2HImmunity to echoes HThe remaining DLL models in Figure 9/G.961 are used to test performance of digital transmission systems in the presence of BTs and/or diameter changes. HIn each model, no errors should be observed in any 15 minutes (provisional) measuring interval when monitoring any Bchannel. HSpecification of data sequences to be used for this measurement are for N* further study. 4.2.4.3HIntrasystem crosstalk HUsing the crosstalk arrangement described in section 4.2.2.2 with simulated crosstalk noise injected in each DLL model in Figure 9/G.961 the observed bit error ratio (BER) should be  10é6 (provisional). HWhen BER measurements are performed in a Bchannel, a measuring interval of at least 15 minutes (provisional) is required. HIn each DLL model, performance margins are determined. Definition of a minimum positive performance margin is left for further study. This is required to account for additional DLL loss due to splices, and environmental effects (e.g. temperature change). HSpecification of data sequences to be used for this measurement are for further study. 4.2.4.4HImpulse noise HFor further study. 4.2.4.5HLongitudinal Voltages Induced from Power Lines HFor further study. 8e%% (3303) CCITT\APIX\DOC\150E4.TXS 87:f:%%(3303) CCITT\APIX\DOC\150E4.TXS 7  5.HTransmission method HThe transmission system provides for duplex transmission on 2wire metallic local lines. Duplex transmission shall be achieved through the use of ECHO CANCELLATION (ECH) or TIME COMPRESSION MULTIPLEX (TCM). With the ECH method, illustrated in Figure 14/G.961, the echo canceller produces a replica of the echo of the transmitted signal that is subtracted from the total received signal. The echo is the result of imperfect balance of the hybrid and impedance discontinuities in the line. HWith the TCM or "burst mode" method, illustrated in Figure 15/G.961, transmissions on the DLL are separated in time (bursts). Blocks of bits (bursts) are sent alternatively in each direction. Bursts are passed through buffers at each transceiver terminal such that the bit stream at the input and output of the TCM transceiver terminal is continuous at the rate R. The bit rate on the line is required to be greater than 2R to provide for an idle interval between bursts which is necessary to allow for the transmission delay and transmitter/receiver turn around (switching of Sn and SR in Figure 15/G.961.  X` HP H   x|@  6'6'StandardC6QMS $=R6'6'StandardC6QMS $=R- Y2*t-  ` `  <  <AP IX150E < YYt*tdv  ` `  <  <AP IX150E < YPM:dv (3303) :QM:f (3303)    6.HActivation/deactivation 6.1HGeneral  `  HThe functional capabilities of the activation/deactivation procedure are specified in Recommendation G.960. The transmission system has to meet  X the requirements specified in Recommendation G.960. In particular, it has to make provision to convey the signals defined in Recommendation G.960 which are required for the support of the procedures. 6.2HPhysical Representation of Signals N*Ԍ HThe signals used in the digital transmission system are system dependent and can be found in Annex A and in the Appendices to this Recommendation. 7.HOperation and Maintenance 7.1HOperation and Maintenance Functions HThe operation and maintenance functions in the digital transmission system using metallic local lines for the ISDN basic rate access, are defined in Recommendation G.960. 7.2HCL Channel 7.2.1 HCLChannel Definition HThis channel is conveyed by the digital transmission system in both directions between LT and NT1. It is used to transfer information concerning operation, maintenance and activation/deactivation of the digital transmission system and of the digital section. 7.2.2HCLChannel Requirements HFor further study. HThe minimum number of functions (optional or mandatory) the CL channel should support is for further study. 7.3HTransfer Mode of Operation and Maintenance Links HFor further study. 8.HPower Feeding 8.1HGeneral HThis section deals with power feeding of the NT1, one regenerator (if required), and the provision of power to the usernetwork interface according to Recommendation I.430 under normal and restricted conditions. HWhen activation/deactivation procedures are applied, power down modes at the NT1, regenerator (if required) and the LT are defined. 8.2HPower Feeding Options HPower feeding options under normal and restricted conditions are considered. For this purpose, a restricted condition is entered after failure of AC mains power at the NT1 location. Ha)  Power feeding of NT1 under normal conditions will be provided using one of the following options:ƀ% H AC mains powering; H  remote powering from the network (or via a regenerator, if required).ƀ% H In both cases the NT1 may provide power to the usernetwork interface N* according to Recommendation I.430. This power is derived from AC mains or remotely from the network.ƀ% Hb)  Power feeding of NT1 under restricted conditions, when provided, employs one of the following optional sources:ƀ% H backup battery; H  Remote powering from the network (or via a regenerator, if required).ƀ% H In both cases the NT1 may provide power to the usernetwork interface according to Recommendation I.430.ƀ% H Power feeding options are chosen to satisfy national regulations.ƀ% 8.3HPower Feeding and Recovery Methods HTwo power feeding and recovery methods are possible and are described in Figure 16/G.961.   HWhen no regenerator is present on the DLL connecting the LT and the NT1, for each case in Figure 16/G.961 the power source could be either a constant voltage source with current limiting or a constant current source with voltage limiting. HWhen a regenerator is present, both methods of power feeding and recovery in Figure 16/G.961 remain applicable. However, when a constant voltage source is used at the LT, the regenerator power sink is connected in parallel to the DLLs and when a constant current source is used at the LT, the regenerator power sink is connected in series with the DLLs. The resulting configurations are shown in Figure 17/G.961. 8.4HDLL Resistance HThis parameter is a particular subject of the individual local network and therefore out of the scope of this Recommendation. Its maximum value depends on the LT output voltage, the power consumption of the NT1 and regenerator (if required) and the power feeding arrangement for the usernetwork interface. 8.5HWetting Current HThe NT1 shall provide a DC termination to allow a minimum wetting current to flow (the value has to be defined) including the power down mode or in case of local power feeding of the NT1. 8.6HLT Aspects HA current limitation for voltage source configuration or a voltage limitation for current source configuration is required. The values shall take into account the relevant IEC Publications and national safety regulations. HShortterm overload of the feeding current may be tolerated (charging condition of the capacitor of DC/DC converter in NT1). 8.7HPower Requirements of NT1 and Regenerator 8.7.1HPower Requirements of NT1 Ha)  active state without powering of usernetwork interface: to be defined;ƀ% Hb)  active state including restricted powering of the usernetwork interface as defined in Recommendation I.430: to be defined;ƀ% Hc)  active state including normal powering of usernetwork interface as defined in Recommendation I.430: to be defined;ƀ% Hd)  power down mode: to be defined.ƀ% 8.7.2HPower Requirements of Regenerator HFor further study. 8.8HCurrent Transient Limitation HThe rate of change of current drawn by the NT1 or regenerator from the network shall not exceed X mA/s. The value of X is to be defined.  (   9.HEnvironmental Conditions 9.1HClimatic Conditions HClimatograms applicable to the operation of NT1 and LT equipment in weather protected and nonweather protected locations can be found in IECPublication7213. The choice of classes is under national responsibility. 9.2HProtection 9.2.1HIsolation HIsolation between various points at the NT1 can be identified: H between line interface and T reference point; H between line interface or T reference point and AC mains (this is generally defined in IEC Guide 105 and IEC Publication 950 but the test requirements may be different in various countries);ƀ% H between line interface and the protective ground of AC mains. 9.2.2HOvervoltage Protection HTo conform with Recommendations K.12, K.20 for LT. HTo conform with Recommendations K.12, K.Y for NT1. 9.3HElectromagnetic Compatibility 9.3.1HHSusceptibility, Radiated and Conducted Emission Levels for LT or NT1 Equipment ƀ%H HThis is outside of the scope of this Recommendation. CISPR Publ. 22 and national regulations have to be considered. 9.3.2HLimitation of the Output Power to the Line HDue to limited longitudinal conversion loss of the line at high frequencies and the limitation of radiation according to CISPR Publ. 22 and national regulations, the output power shall be limited. The specific values are outside the scope of this Recommendation.   %ANNEX A ( (to Recommendation G.961) (  General Structure for an Appendix on Electrical Characteristicsă A.HElectrical Characteristics HShort general characterization of the digital transmission system. Note The content of this Annex is a guideline for the presentation of the description of the digital transmission systems and is not intended to constrain any of the systems which will be included. A.1HLine Code HFor both directions of the transmission the line code is .... And the coding scheme will be ... A.2HSymbol Rate HThe symbol rate is determined by the line code, the bit rate of the information stream and the frame structure. The symbol rate is ...kBaud. A.2.1HClock Requirements A.2.1.1HNT1 Free Running Clock Accuracy HThe accuracy of the free running clock in the NT1 shall be  ... ppm. A.2.1.2HLT Clock Tolerance HThe NT1 and LT shall accept a clock accuracy from the ET of  ... ppm. A.3HFrame Structure HThe frame structure contains a frame word, N times (2B+D) and a CL channel. H        Frame word  N times (2B+D)  CL channel        A.3.1HFrame Length HThe number N of (2B+D) slots in one frame is ... A.3.2HBit Allocation in Direction LTNT1 HIn Figure A1/G.931 the bit allocation is given. HFigure A1/G.931 bit allocation in direction LTNT1. V' A.3.3HBit Allocation in Direction NT1LT HIn Figure A2/G.931 the bit allocation is given. HFigure A2/G.961 bit allocation in direction NT1LT. A.4HFrame Word HThe frame word is used to allocate bit positions to the 2B+D+CL channels. It may, however, also be used for other functions. A.4.1HFrame Word in Direction LTNT1 HThe code for the frame word will be ... A.4.2HFrame Word in Direction NT1LT HThe code for the frame word will be ... A.5HFrame Alignment Procedure A.6HMultiframe HTo enable bit allocation of the CL channel in more frames next to each other a multiframe structure may be used. The start of the multiframe is determined by the frame word. The total number of frames in a multiframe is ... A.6.1HMultiframe Word in Direction NT1LT HThe multiframe will be identified by ... A.6.2HMultiframe Word in Direction LTNT1 HThe multiframe will be identified by ... A.7HFrame Offset between LTNT1 and NT1LT Frames HThe NT1 shall synchronize its frame on the frame received in the direction LT to NT1 and will transmit its frame with an offset. A.8HCL Channel A.8.1HBit rate A.8.2HStructure A.8.3HProtocols and Procedures A.9HScrambling HScrambling will be applied on 2B+D channels and the scrambling algorithm shall be as follows: HIn direction LT to NT1 HIn direction NT1 to LT. ( A.10HActivation/Deactivation HDescription of system activation/deactivation procedure including options that are supported and options that are not supported. HSee also CCITT Recommendation AA, section 5. A.10.1HSignals used for Activation HA list and definition of the signals used for activation/deactivation (SIGs). H signals used for startup (CL not available) H bits in CL channel in an already established frame. A.10.2HDefinition of Internal Timers HHA.10.3HDescription of the Activation Procedure (based on arrow sequence for the errorfree case)ƀ%H H activation from the network side H activation from the user side HHA.10.4HState transition table NT1 as a function of INFOs, SIGs, internal timers ƀ%H HThe description of loop backs and options supported is given in such a way, that the minimum implementation may be clearly identified.  Xh HHA.10.5HState transition table LT as a function of FEs, SIGs, internal timersp&H HThe description of loop backs and options supported is given in such a way, that the minimum implementation may be clearly identified. A.10.6HActivation times HSee CCITT Recommendation AA,  5.5.1 and 5.5.2. A.11HJitter HJitter tolerances are intended to ensure that the limits of CCITT Recommendation I.430 are supported by the jitter limits of the transmission system on local lines. The jitter limits given below must be satisfied regardless of the length of the local line and the inclusion of one regenerator, provided that they are covered by the transmission media characteristics (see section 3). The limits must be met regardless of the bit patterns in the B, D and CL channels. A.11.1HNT1 Input Signal Jitter Tolerance HThe NT1 shall meet the performance objectives with wander/jitter at the maximum magnitudes (J1, J2) indicated in Figure A.3/G.961, for single jitter frequencies in the range of F1 Hz to F3 kHz (F3 = 1/4 F6, F6 = symbol rate frequency), superimposed on the test signal source. The NT1 shall also meet the performance objectives with wander per day of up to ...UI peaktopeak where the maximum rate of change of phase is ...UI/hour. ( A.11.2HNT1 Output Jitter Limitations HWith the wander/jitter as specified in A.11.1 superimposed on the NT1 input signal, the jitter on the transmitted signal on the NT1 towards the network shall conform to the following: Ha)  The jitter shall be equal to or less than .... UI peaktopeak and less than ...UI r.m.s. when measured with a highpass filter have a 20 dB/decade rolloff below M.F2 Hz (M  1).p& Hb)  The jitter in the phase of the output signal relative to the phase of the input signal (from the network) shall not exceed ....UI peaktopeak or ....UI r.m.s. when measured with a bandpass filter have a 20 dB/decade rolloff above N.F2 Hz (N2) and a 20dB/decade rolloff below K.Fk (Fk << 1). This requirement applies with superimposed jitter in the phase of the input signal as specified in A.11.1 for single frequencies up to F2 Hz.p& A.11.3HTest Conditions for Jitter Measurements HDue to bidirectional transmission on the 2wire and due to severe intersymbol interference no well defined signal transitions are available at the NT1 2wire point.  T Noteĩ Two possible solutions are proposed: Ha)  A test point in the NT1 is provided to measure jitter with an undisturbed signal.p& Hb)  A standard LT transceiver including an artificial local line is defined as a test instrument.p& A.12HTransmitter Output Characteristics of NT1 and LT HThe following specifications apply with a load impedance of .... A.12.1HPulse Amplitude HThe zero to peak nominal amplitude of the largest pulse shall be ....V and the tolerance shall be  ....%. A.12.2HPulse Shape HThe pulse shape shall meet the pulse mask of Figure .... A.12.3HSignal Power HThe average signal power shall be between ....dBm and ....dBm. A.12.4HPower Spectrum HThe upper bound of the power spectral density shall be within the template in Figure .... A.12.5HTransmitter Signal Nonlinearity HThis is a measure of the deviations from ideal pulse heights and the individual pulse nonlinearity. HThe measurement method is for further study. A.13HTransmitter/Receiver Termination A.13.1HImpedance HThe nominal input/output impedance looking toward the NT1 or LT respectively shall be .... A.13.2HReturn Loss HThe return loss of the impedance shall be greater than shown in the template Figure .... ::QL (3303) (CCITT\APIX\DOC\150E5.TXS) :9:Q:Q7(3303) (CCITT\APIX\DOC\150E5.TXS) 9 X A.13.3HLongitudinal Conversion Loss HThe minimum longitudinal conversion loss shall be as follows: H....kHz....dB H....kHz....dB 8 Appendices I to IV 8) +Ԍ8(to Recommendation G.961) HThe text of these Appendices has not been included in the final report, but will be printed in the Blue Book at the appropriate place. A.14HNew Supplements Nos. 35 and 36 HSupplement No. 35 Guidelines concerning the measurement of wander H(Contribution from United States of America, referred to in Recommendations G.812 and G.824.) HSupplement No. 36 Jitter and wander accumulation in digital networks H(Referred to in Recommendation G.824.) HThe text of these supplements has not been included in the final report, but will be printed in the Blue Book at the appropriate place. 8$