CS-03, Part VII — Requirements for Limited Distance Modems and Digital Subrate Terminal Equipment

3.2.3 Average Power

3.2.3.1 Requirement

The average output power when a random signal sequence, (0) or (1) equiprobable in each pulse interval, is being produced as measured across a 135 ohm resistance shall not exceed 0 dBm for 9.6 kbps or +6 dBm for all other rates (2.4 kbps, 4.8 kbps, 19.2 kbps, 38.4 kbps, 56 kbps and 64 kbps).

3.2.3.2 Method of Measurement

  1. Connect the TE to the test circuit of Figure 3.2.3.
  2. Arrange the TE to transmit a pseudo random signal sequence.
  3. Measure the power of the transmitted signal.
  4. Repeat the test at all of the transmission rates of the TE.
Figure 3.2.3: Subrate – Average Power
Figure 3.2.3: Subrate – Average Power

[Description of Figure]

Note: The measuring instrument should provide a high-impedance, balanced input with adequate bandwidth. All resistors are ±1% tolerance, 1 W.

3.2.4 Encoded Analog Content

3.2.4.1 Requirement

  1. If the TE that is for connection to subrate services contains an analog-to-digital converter, or generates signals directly in digital form which are intended for eventual conversion into voice band signals, the encoded analog content must be limited. The maximum equivalent power of encoded analog signals shall be limited as specified below when derived by a zero level decoder and averaged over a 3-second time period.
    1. -3 dBm for network control signals
    2. -6 dBm for V.90 or V.92 modems
    3. -9 dBm for all other signals other than live voice
  2. TE providing through transmission capability to other public switched telephone network (PSTN) connections shall meet the requirements of Table 3.2.4.

Note: All limits are with reference to 600 ohms.

3.2.4.2 Method of Measurement

  1. Connect the TE to the test circuit of Figure 3.2.4. As shown, two types of signals may be transmitted:
    1. internally generated signals that are generated directly in digital form and are intended for eventual conversion to analog form; and
    2. internally generated analog signals that are converted to digital format for eventual reconversion to analog form.
  2. For signals of type (a) or (b) as described above, set the equipment to generate each of the possible signals.
  3. Record the power of each of the transmitted signals as measured at the output of the zero level decoder or companion TE. The recorded level shall be the maximum attainable when averaged over any 3-second interval.
Table 3.2.4 – Allowable Net Amplification Between Ports
TO Tie Trunk Type Ports Integrated Services Trunk Ports Off-premises Station Ports (2-Wire) Analog Public Switched Network Ports (2-Wire) Subrate 1.544 Mbps Digital PBX-CO Trunk Ports (4-Wire)
FROM Lossless 2/4-Wire Subrate 1.544 Mbps Satellite (4-wire) Subrate 1.544 Mbps Tandem(4-wire)
Lossless Tie Trunk Port (2/4 wire) dB dB dB dB dB - -
Subrate 1.544 Mbps Satellite Tie Trunk Port (4-wire) dB - dB dB dB - -
Subrate 1.544 Mbps Tandem Tie Trunk Port (4-wire) -2 dB dB dB dB dB - -
Integrated Services Trunk Ports -2 dB dB dB dB dB - -
Registered Digital TE -2 dB dB dB dB dB dB dB
On-premises Station Port with Registered TE -2 dB dB dB dB dB dB dB
Off-premises Station Port (2-wire) dB dB dB dB dB dB dB
Analog Public Switched Network Ports (2-wire) - - - - dB dB -
Subrate 1.544 Mbps Digital PBX-CO Trunk Ports (2-Wire) - - - - dB - -

Notes:

  1. The source impedance for all measurements shall be 600 ohms. All ports shall be terminated in appropriate loop or private line channel simulator circuits or 600 ohm terminations.
  2. These ports are for 2-wire on-premises station ports to separately registered TE.
  3. These through gain limitations are applicable to multi-port systems where channels are not derived by time or frequency compression methods. TE employing such compression techniques shall assure that equivalent compensation for through gain parameters is evaluated and included in the test report.
  4. TE and network protection devices may have net amplification exceeding the limitations of this subsection provided that, for each network interface type to be connected, the absolute signal power levels specified in this section are not exceeded.
  5. The indicated gain is in the direction which results when moving from the horizontal entry toward the vertical entry.
  6. TE or network protection devices with the capability for through transmission from voice band private line channels or voice band metallic channels to other telephone network interfaces shall ensure that the absolute signal power levels specified in this section, for each telephone network interface type to be connected, are not exceeded.
  7. TE or network protection devices with the capability for through transmission from voice band private line channels or voice band metallic private line channels to other telephone network interfaces shall ensure, for each telephone network interface type to be connected, that signals with energy in the frequency band 2450-2750 Hz are not through transmitted unless there is at least an equal amount of energy in the band 800-2450 Hz within 20 milliseconds of application of the signal.
Figure 3.2.4: Subrate – Encoded Analog Content
Figure 3.2.4: Subrate – Encoded Analog Content

[Description of Figure]

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3.2.5 Equivalent power spectral density (PSD) for Maximum Output

When applied to a 135 ohm resister, the instantaneous amplitude for the PSD, obtainable from the registered terminal equipment, shall not exceed the PSD defined by the following limited function, in dBm/Hz:

formula

[Description of image]

where "A" is equal to 1/2 for 9.6 kbps and 12.8 kbps or 1 for all other rates; "fbaud" is equal to the baud rate; "f3dB" is equal to 1.3 times the baud rate times 1.05; "f" is the frequency; and "k" is defined in Table 3.2.5. Additional attenuation is required at certain baud rates in the bands specified in Tables 3.2.2(a) and 3.2.2(b). The PSD shall be measured for frequencies between 1/2 the baud rate and 20 times the baud rate. If 20 times the baud rate is less than 80 kHz, then the upper frequency measurement bound shall be 80 kHz. The resolution bandwidth for the PSD shall be less than or equal to 0.1 times the baud rate, but no greater than 3 kHz.

Table 3.2.5 – Values for k and Average Output Power
User Data Rate (kbps) Line Rate (R) (kbps) Values for k Maximum Average Power (dBm)
2.4 2.4 0.00727798 6
4.8 4.8 0.00727798 6
9.6 9.6 0.00727798 6
19.2 19.2 0.00727798 0
38.4 38.4 0.00727798 6
56 56 0.00727798 6
64 64 0.00727798 6

3.2.6 Limitations on TE Connected to PSDS (Types I, II and III)

If the PSDS (Types I, II and III) TE contains an analog-to-digital converter or generates signals directly in digital form that are intended for eventual conversion into voice band analog signals, the encoded analog content of the digital signal shall be limited as specified in Section 3.2.4.

  1. For the PSDS (Type II) TE, the pulse repetition rate shall be a maximum of (144,000 ± 5) pulses per second; for the PSDS (Type III) TE, the pulse repetition rate shall be a maximum of (160,000 ± 5) pulses per second.
  2. When applied to a 135 ohm resistor, the instantaneous amplitude of the largest isolated output pulse obtainable from the approved terminal equipment shall fall within the template as shown in Table 3.2.6 below for the PSDS Type II or for the PSDS Type III. The limiting pulse template shall be defined by passing an ideal 50% duty cycle rectangular pulse within the amplitude/pulse rate characteristics shown below through a 1-pole low-pass filter with a -3 dB frequency of 260 kHz.
Table 3.2.6 – Maximum Output Pulse for PSDS Type II and PSDS Type III TE
Pulse Characteristic Template PSDS Type II PSDS Type III
Pulse Height 2.6 V ± 5% 2.4 V ± 5%
Pulse Width (3472.2 ± 150) ns (3125 ± 100) ns
Maximum Rise or Fall Time – (from 10% to 90%) 100 ms (1.2 ± 0.2) μs

3.2.7 Signalling Interference

3.2.7.1 Requirements

TE registered for connection to DS services shall not deliver digital signals to the telephone network with encoded analog energy in the frequency band 2450-2750 Hz unless at least an equal amount of encoded analog energy is present in the frequency band 800-2450 Hz.

3.2.7.2 Method of Measurement

The TE shall be active and transmitting the encoded analog signal. The test shall be performed on each of the internally generated signals other than DTMF signals.

  1. Connect the TE to the test circuit of Figure 3.2.7. As shown, two types of signals may be transmitted:
    1. internally generated signals that are generated directly in digital form, but which are intended for eventual conversion to analog form; and
    2. internally generated analog signals that are converted to digital format for eventual reconversion to analog form.
  2. For signals of type (a) or (b) as described above, set the equipment to generate each of the possible signals.
  3. Read the signal energy in the frequency band 800-2450 Hz.
  4. Read the signal energy in the frequency band 2450-2750 Hz.
  5. Repeat steps (3) and (4) for each possible signal.
Figure 3.2.7: Subrate – Signalling Interference
Figure 3.2.7: Subrate – Signalling Interference

[Description of Figure]

Note: The spectrum analyzer should provide the correct termination for tip and ring leads via a high-impedance balanced input across a 600 ohms resistive load or via an appropriate BALUN.

3.2.8 On-Hook Level

3.2.8.1 Requirements

DS TE shall comply with the following:

  1. The power transmitted to the telephone network in the on-hook state as derived by a zero level decoder shall not exceed -55 dBm equivalent power for digital signals within the frequency bank from 200 to 4000 hertz. Network protective devices shall also ensure that, for any input level up to 10 dB above the maximum level that is expected under normal operation, the power to a zero level decoder does not exceed the above limits.
  2. The power derived by a zero level decoder, in the on-hook state, by reverse battery equipment, shall not exceed -55 dBm unless the equipment is arranged to inhibit incoming signals.

3.2.8.2 Method of Measurement

  1. Connect the TE to the test circuit as indicated in Figure 3.2.8.
  2. Set the digital equipment to transmit the on-hook signal.
  3. Measure the analog transmitted signal power at the output of the band pass filter.
Figure 3.2.8: Subrate – On-hook Level
Figure 3.2.8: Subrate – On-hook Level

[Description of Figure]

Note: The spectrum analyzer should provide the correct termination for tip and ring leads via a high-impedance balanced input across a 600 ohms resistive load or via an appropriate BALUN.

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3.2.9 Transverse Balance Limitations

3.2.9.1 Requirement

The metallic to longitudinal balance coefficient, transverse balance is expressed as:

BALANCE M-L (dB) = 20 log10 (VM /VL)

Where VL is the longitudinal voltage produced across a 500 ohm longitudinal termination and vM is a metallic voltage across the tip and ring connection of the TE when a voltage (at any frequency between f1 < f < f2, see Table 3.2.7) is applied from a balanced source with a metallic source impedance of 135 ohms. The source voltage should be set such that vM= .367 volts when a termination of 135 ohms is substituted for the TE.

An illustrative test circuit that satisfies the above conditions is shown in Figure 3.2.9(b); other means may be used to determine the transverse balance coefficient specified herein, provided that adequate documentation of the appropriateness, precision, and accuracy of the alternative means is provided by the applicant. The minimum transverse balance requirements for TE connected to digital services shall be equalled or exceeded for the range of frequencies applicable for the equipment under test and under all reasonable conditions of the application of earth ground to the equipment. All such TE shall have a transverse balance in the acceptable region of Figure 3.2.9(a) for the range of frequencies shown in Table 3.2.7 for the specified digital service in question. The metallic impedance used for the transverse balance measurements for all subrate services shall be 135 ohms. The longitudinal termination for subrate services less than 12 kbps shall be 500 ohms and, for subrates greater than 12 kbps, the longitudinal termination shall be 90 ohms.

Figure 3.2.9(a): Transverse Balance Requirements
Figure 3.2.9(a): Transverse Balance Requirements

[Description of Figure]

Table 3.2.7 – Frequency Ranges of Transverse Balance Requirement
Service (kbps) Lower Frequency (Hz) Upper Frequency (Hz) Longitudinal Termination (ohms) Metallic Termination (ohms)
2.4 200 2.4 500 135
4.8 200 4.8 500 135
9.6 200 9.6 500 135
19.2 200 19.2 500/90 135
38.4 200 38.4 500/90 135
56 200 56 500/90 135
64 200 64 500/90 135
Figure 3.2.9(b): Transverse Balance
Figure 3.2.9(b): Transverse Balance

[Description of Figure]

T1 135 Ω: 135 Ω C.T. Wide band transformer
C1 2.4 to 24.5 pF Differential trimmer
RL Longitudinal termination from Table 3.2.7
RCAL 135 Ω
R1 Selected so that R1 ± 1% tolerance, 1 W.

3.2.9.2 Method of Measurement

TE may require special attention to ensure that it is properly configured for this test. For example, if the equipment would normally be connected to an AC power ground, a cold-water-pipe ground, or if it has a metallic or partially metallic exposed surface, these points shall be connected to the test ground plane. Similarly, if the TE provides connections to other equipment through which ground may be introduced to the equipment, these points shall be connected to the test ground plane. Equipment which does not contain any of these potential connections to ground shall be placed on a conductive plate which is connected to the test ground plane. This applies to both non-powered and AC-powered equipment.

  1. Connect the TE to the test circuit as indicated in Figure 3.2.9(b), with the calibration test resistor (135 ohms) in place.
  2. Set the spectrum analyzer and tracking generator to the appropriate frequency ranges:
    1. for 2.4 kbps subrate TE - 200 Hz to 2.4 kHz;
    2. for 4.8 kbps subrate TE - 200 Hz to 4.8 kHz;
    3. for 9.6 kbps subrate TE - 200 Hz to 9.6 kHz;
    4. for 19.2 kbps subrate TE - 200 Hz to 19.2 kHz;
    5. for 38.4 kbps subrate TE - 200 Hz to 38.4 kHz;
    6. for 56.0 kbps subrate TE - 200 Hz to 56.0 kHz; and
    7. for 64.0 kbps subrate TE - 200 Hz to 64.0 kHz.
  3. Adjust the tracking generator voltage to measure 0.367 V across the calibration test resistor.
  4. Connect the spectrum analyzer across the longitudinal resistor RL (90 ohms or 500 ohms, per Table 3.2.7).
  5. Adjust the capacitor C1 until a minimum voltage across the resistor RL is obtained. This represents the highest degree to which the bridge can be balanced. The result of this balance calibration shall be at least 20 dB better than the requirement for the applicable frequency band. If this degree of balance cannot be attained, further attention should be given to component selection for the test circuit and its construction.
  6. Reverse the polarity of the tip and ring pair under test. If the longitudinal voltage (VL) changes by less than 1 dB, the calibration is acceptable. If the longitudinal voltage changes by more than 1 dB, it indicates that the bridge needs further adjustment to accurately measure the balance of the TE. Repeat the calibration process until the measurements differ by less than 1 dB while maintaining the balance noted in step (5) above.
  7. Replace the calibration resistor with one tip and ring pair of the TE.
  8. Measure the voltage across the tip and ring of the TE; this is the metallic reference voltage (VM).
  9. Measure the voltage across the resistor RL; this is the longitudinal voltage (VL).
  10. Calculate the balance using the following formula:

    BALANCE (dB) = 20 log10 (VM/VL)

    Note: If the readings are, for example, taken in dBV, then the equation may be simplified as follows:

    Balance (dB) = VM (dBV) – VL (dBV)
  11. Reverse the tip and ring connections of the TE and repeat steps (8) through (10). The lesser of the two results is the longitudinal balance of this pair of the TE.
  12. Connect the other tip and ring pair of the TE to the balance test set.
  13. Repeat steps (8) through (11) for this pair.

4.0 LDM Loop Simulator for Metallic Voltage Tests

The loop simulator circuits to perform the tests described in Section 3.0 are shown in schematic form in this section.

Figure 4.0: LDM Loop Simulator for Metallic Voltage Tests
Figure 4.0: LDM Loop Simulator for Metallic Voltage Tests

[Description of Figure]

Resistances (ohms), Capacitances (uF), Tolerances ± 2%. RV + RP = 50 through 3000 ohms.
ZP is the magnitude of the low-pass filter impedance, which is {25 ohms DC;}3 kohms from 10 Hz to 6 kHz.
RP/2 = DC resistance of low-pass filter, ZP in parallel with 428.7 ohms.

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