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CS-03, Part VI — Requirements for Integrated Services Digital Network Terminal Equipment

3.4 Transverse Balance at U Reference Point

3.4.1 Requirement

TE intended to connect to ISDN access, either BRA or PRA, at the U reference point shall comply with the following requirements:

The transverse balance at the network interface shall equal or exceed the minimum values shown in Figure 3.4(a) at all frequencies as specified, under all reasonable applications of earth ground to the TE. Transverse balance is defined as: 20 log10 (VM/VL).

For the purpose of this section, 1.544 Mbps = 1.544 MHz.

Figure 3.4(a): Transverse Balance Requirements at the U Reference Point
Figure 3.4(a): Transverse Balance Requirements at the U Reference Point

[Description of figure]

3.4.2 Method of Measurement

  1. Connect the TE as shown in Figure 3.4(b).
  2. Set the spectrum analyzer/tracking generator to sweep the appropriate frequency range:
    1. for BRA: 200 Hz to 192 kHz;
    2. for PRA: 12 kHz to 1.544 MHz.
  3. Adjust the tracking generator voltage to measure -10 dBV (316 mV) across the calibration test resistor RCAL.
  4. Connect the detector across the longitudinal resistor RL (RL = 500 ohms for frequencies < 12 kHz, and 90 ohms for frequencies > 12 kHz).
  5. Adjust capacitor C1 until a minimum voltage across resistor RL is obtained. This represents the highest degree to which the bridge can be balanced. This balance measurement must 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 the component selection and the construction of the test circuit.
  6. Reverse the polarity of the tip and ring leads of the TE being tested, using switch S2. 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, the bridge needs further adjustment to be sufficiently balanced to accurately measure the TE. Repeat the calibration process until the measurements differ by less than 1 dB while maintaining the 20 dB minimum balance noted in step (5) above.
  7. Replace the calibration resistor with 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 resistor RL. This is the longitudinal voltage (VL).
  10. Calculate the balance using the following formula:

    Balance M/L (dB) = 20 log10 (VM/VL)

Notes:

  1. If the readings are taken in dBV, the equation can be simplified as follows:

    Balance M/L (dB) = VM(dBV) - VL (dBV)
  2. TE which is not normally grounded should be set in its normal rest position directly on a grounded plane whose overall dimensions are at least 50% greater than the footprint of the TE. From a transverse balance standpoint, this represents a worst case condition (i.e. the closest proximity to ground is likely to be encountered by the TE).
Figure 3.4(b): Transverse Balance Bridge for Basic and Primary Rate Access
Figure 3.4(b): Transverse Balance Bridge for Basic and Primary Rate Access

[Description of figure]

Notes:

  1. A 3pF capacitance may be required between tip to ground or ring to ground depending on bridge construction.
  2. Use a transformer with an appropriate frequency response for the frequency band under test.
  3. The combined impedance of the 50 ohm generator plus R1 shall equal the nominal impedance of the device under test.
  4. Use an RCAL value of 100 ohms for 1.544 Mbps devices and 135 ohms for BRA devices.
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3.5 Transmitted Encoded Analog Signals

3.5.1 General

The requirements of this section apply to ISDN TE that performs analog-to-digital conversion for other than live voice signals, or that generates signals directly in digital form which will be decoded to voice band analog signals in the network. These requirements ensure that, when such signals are decoded in the network, no network harm will occur due to high signal levels, restricted frequencies, etc.

When such encoded analog signals are decoded in accordance with the specifications for the µ255 PCM encoding law, which are set forth in ITU-T Recommendation G.711, the signals shall comply with the requirements of this section. The requirements of this section do not apply to ISDN terminal interfaces which transmit digital signals that do not contain encoded analog signals.

3.5.2 Transmitted Encoded Analog Signal Power – Access Facilities

3.5.2.1 Requirement

  1. The maximum equivalent power of encoded analog signals at the network interface, as derived by a zero-level decoder on any B-channel, shall not exceed the following limits:
    1. dBm when averaged over 250 ms for all signals other than live voice and dual tone multi-frequency (DTMF) signals;
    2. -3 dBm for DTMF signals when averaged over 3 seconds;
    3. -6 dBm for V.90 or V.92 modem signals when averaged over 3 seconds; and
    4. -9 dBm for all other signals other than live voice when averaged over 3 seconds.

Notes:

  1. All limits are in reference to a 600 ohms resistor.
  2. TE providing through transmission capability to other public switched network connections shall meet the requirements of Table 3.5.2.
Table 3.5.2 - 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 (4-wire)
From Lossless 2/4-wire Subrate 1.544 Mbps Satellite (4-wire) Subrate 1.544 Mbps Satellite (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 (4-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. The above 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 NPD 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 and NPD with the capability for through transmission from voice band private line channels or voice band metallic channels to other telephone network interfaces must not exceed the absolute signal power levels specified in this section for the telephone network interface type to be connected.
  7. TE and NPD 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 frequency band 800-2450 Hz within 20 milliseconds of application of the signal.

3.5.2.2 Method of Measurement

  1. Connect the TE to the test circuit as shown in Figure 3.5(a). Select a B channel output from the B channel decoder.
  2. Set the filter cut-off frequencies to achieve a 100 Hz to 4000 Hz pass band and arrange the spectrum analyzer to read power in dBm averaged over 3 seconds.
  3. Operate the TE at maximum gain to transmit each of its possible output signals other than live voice, including voice band data signals. If the TE has input interfaces for connection to registered analog terminals, apply a white noise test signal at -9 dBm at such interfaces.
  4. Record the maximum power level reading in dBm.
  5. Calculate the gain of the through transmission path from the output level measured in step (4) to the input level set in step (3).
  6. Arrange the spectrum analyzer to read power averaged over 250 milliseconds. Repeat steps (3) and (4).
Figure 3.5(a): Measurement of Transmitted Encoded Analog Signal Power

Figure 3.5(a): Measurement of Transmitted Encoded Analog Signal Power

[Description of figure]

R = 600 ohms ± 1%, 1W.

Notes:

  1. The B channel decoder enables the following functions:
    1. operates the D channel to satisfy the TE operating requirements;
    2. provides separate outputs from the B channel; and
    3. provides a stable clock to operate the TE.
  2. The spectrum analyzer should provide the correct termination for tip and ring leads via a high impedance balanced input across 600 ohms resistive load or via an appropriate BALUN.

3.5.3 Encoded Analog Equivalent Audio Signal Limiting

The applicable technical requirements and methods of measurement for audio signal limiting are outlined in CS-03 Part I, Section 3.4.8.

3.5.4 Encoded Analog Equivalent Signalling Interference

3.5.4.1 Requirement

The equivalent power of encoded analog signals at the network interface for other than live voice, as derived by a zero level decoder delivered by the TE for the first 2 seconds in response to an incoming alerting signal (by analogy "off-hook" in PSTN) on any B channel, in the frequency band 2450-2750 Hz, shall be less than the power present simultaneously in the frequency band 800-2450 Hz. The gain in the frequency band 2450-2750 Hz shall not exceed by more than 1 dB the gain present in the frequency band 800-2450 Hz.

If the signal power in the frequency band 2450-2750 Hz is less than -44 dBm, this requirement does not apply.

3.5.4.2 Method of Measurement

  1. Connect the TE to the test circuit as shown in Figure 3.5(b).
  2. Connect and select the B channel on the TE.
  3. Record the maximum power value in dBm that occurs during the first 2 seconds after the B channel connected state is obtained, for each of the possible output signals in step (4).
  4. Set the TE to transmit each of its possible output signals.
  5. Record the maximum power value obtained.
Figure 3.5(b): Single Frequency Restriction Measurement
Figure 3.5(b): Single Frequency Restriction Measurement

[Description of figure]

R = 600 ohms ± 1%, 1W.

Notes:

  1. The B channel decoder enables the following functions:
    1. operates the D channel to satisfy the TE operating requirements;
    2. provides separate outputs from the B channel; and
    3. provides a stable clock to operate the TE.
  2. The spectrum analyzer should provide the correct termination for tip and ring leads via a high impedance balanced input across 600 ohms resistive load or via an appropriate BALUN.
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