CS-03, Part II — Requirements for Terminal Equipment Intended for Connection to 1.544 Mbps (DS-1) Digital Interfaces

3.6 Encoded Analog Equivalent Requirements

3.6.1 Idle Sequence Signals

3.6.1.1 Requirements

For connections to 1.544 Mbps digital services, the permissible code words for unequipped µ255 encoded subratechannels are limited to those corresponding to signals of either polarity ofmagnitude equal to or less than X48, where the code word Xn is derived by:

Xn = (255 − n) base 2
−Xn = (127 − n) base 2

3.6.1.2 Demonstration of Compliance

Demonstration of compliancewith the requirement in Section 3.6.1.1 shall be by means of an engineeringattestation that fully describes the individual parameter requirements of Section3.6 and shallstate as a minimum that the design of the TE complies with each requirement ofthis section under all operating conditions.

3.6.2 Metallic AC Energy

3.6.2.1 On-hook Requirements

  1. The power delivered to the 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 band from 200 to 4000 Hz.
  2. Network protective circuitry 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.
  3. Reverse battery interface: 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.

3.6.2.2 Method of Measurement

  1. Connect the TE to the test circuit of Figure 3.6(a).
  2. Ensure that the channel under test is in the on-hook state.
  3. If the equipment provides for connection and throughput of signals from non-registered signal sources, provide a 1000 Hz input signal to the TE at a level up to 10 dB above the maximum level that is expected under normal operation.
  4. Measure the signal power as derived at the output of the zero level decoder or companion TE.
Figure 3.6(a): 1.544 Mbps On-hook Level Measurement
Figure 3.6(a): 1.544 Mbps On-hook Level Measurement

[Description of Figure]

Note: The spectrum analyzer should providethe correct termination for 600 ohms, a high-impedance balanced input with aresistor or an appropriate BALUN.

3.6.3 Encoded Analog Equivalent Transmitted Signal

3.6.3.1 Encoded Analog Content Requirements

  1. If the TE connected to 1.544 Mbps digital service 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 of the subrate channels within the 1.544 Mbps signal must be limited. The maximum equivalent power of encoded analog content as derived by a zero level decoder test configuration shall be limited as specified below when averaged over any 3-second interval.
    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 network connections shall meet the requirements of Section 3.6.5.1.

Note 1: The zero level decoder shall comply with the µ255 PCM encoding law as specified in ITU-T (CCITT) Rec. G.711for voice band encoding and decoding.

Note 2: All limits are in reference to a 600 ohms resistor.

3.6.3.2 Method of Measurement

  1. Connect the TE to the test circuit of Figure 3.6(b). As shown, two types of signals may be transmitted:
    1. internally generated signals which are intended for eventual conversion to analog form; or
    2. internally generated analog signals that are converted to digital format for eventual reconversion to analog form.
  2. For signals of type (a) or type (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 should be the maximum obtainable level when averaged over any 3-second interval.
Figure 3.6(b): 1.544 Mbps Encoded Analog Content Measurement
Figure 3.6(b): 1.544 Mbps Encoded Analog Content Measurement

[Description of Figure]

Note: The spectrum analyzer should providethe correct termination for 600 ohms, a high-impedance balanced input with aresistor or an appropriate BALUN.

3.6.4 EncodedAnalog Equivalent Signalling Interference

3.6.4.1 Requirements

The signal power deliveredto the network interface by the TE and from signal sources internal to network protection devicesin the frequency band 2450-2750 Hz shall be less than or equal to the power present simultaneously in the frequency band 800-2450 Hz for the first 2 seconds after switching to the off-hook state.

3.6.4.2 Method of Measurement

  1. Connect the TE to the test circuit of Figure 3.6(c). 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; or
    2. internally generated analog signals that are converted to digital format for eventual reconversion to analog form.
  2. For signals of type (a) or type (b) as described above, set the TE to generate each of the possible signals in the first 2 seconds after the TE goes off-hook.
  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 3.6(c): 1.544 Mbps Signalling Interface Measurement
Figure 3.6(c): 1.544 Mbps Signalling Interface Measurement

[Description of Figure]

Note: The spectrum analyzer should providethe correct termination for 600 ohms, a high-impedance balanced input with a resistor or an appropriate BALUN.

3.6.5 Through Transmission Paths

3.6.5.1 Requirements

TE havingthrough transmission paths from analog or digital interfaces to digitalinterfaces shall comply with the following requirements:

  1. TE which is capable of connecting an analog interface of a type not shown in Table 3.6 to an outgoing digital trunk or tie trunk interface may insert gain provided that the transmitted signal power limits of Section 3.6.3 are met.
  2. The through transmission gain over the frequency band below 3995 Hz shall comply with the requirements shown in Table 3.6 where the maximum allowable net amplification between interfaces is shown. Positive (+) values denote a gain; negative (−) values denote loss in dB.
  3. Interfaces which have no through transmission path to the public switched network are exempted from these through transmission path requirements.
  4. 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.
  5. The TE shall have no user accessible adjustments that allow these parameter limits to be exceeded.
Table 3.6 - AllowableNet 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 Loss less 2/4-wire Subrate 1.544 Mbps Satellite (4-wire) Subrate 1.544 Mbps Tandem (4-wire)
Lossless Tie Trunk Port (2/4-wire) 0 dB 2 dB 2 dB 2 dB 2 dB - -
Subrate 1.544 Mbps Tandem Tie Trunk Port (4-wire) 1 dB - 3 dB 3 dB 3 dB - -
Subrate 1.544 Mbps Tandem Tie Trunk Port (4-wire) -2 dB 0 dB 0 dB 0 dB 0 dB - -
Integrated Services
Trunk Ports		 -2 dB 0 dB 0 dB 0 dB 0 dB - -
Registered Digital TE -2 dB 0 dB 0 dB 0 dB 0 dB 0 dB 0 dB
On-premises Station Port with Registered TE -2 dB 0 dB 0 dB 0 dB 0 dB 0 dB 0 dB
Off-premises Station Port (2-wire) 2 dB 4 dB 4 dB 4 dB 4 dB 4 dB 4 dB
Analog Public Switched Network Ports (2-wire) - - - - 3 dB 3 dB -
Subrate 1.544 Mbps Digital PBX-CO Trunk Ports (4-wire) - - - - 0 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 ensure 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 are not exceeded for each telephone network interface type to be connected.
  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 frequency band 800-2450 Hz within 20 milliseconds of application of the signal.

3.6.5.2 Method of Measurement

Port to Port Amplification

  1. Connect the digital TE with through ports embedded in the 1.544 Mbps system to the test circuits as shown in figures 3.6(d) and 3.6(e). Establish a connection between the ports under test.
  2. Set switch S1 to position "A." Adjust the filter to pass the band of frequencies below 3995 Hz.
    Note: If the TE is band-limited, then appropriate filter adjustment shall be made.
  3. Establish a through transmission connection in the direction of the network interface under test.
  4. Set the output level of the white noise source so that the spectrum analyzer indicates -11 dBV. This level is to be maintained for all tests.
  5. Set switch S1 to position "B" and measure the signal present at the output side of the TE.
  6. Calculate the gain of the through transmission path, from the input level set in step (4) and the output level measured in step (5).
  7. Repeat steps (1) through (6) for the opposite direction of transmission of the TE if applicable.
  8. Repeat steps (2) through (7) for each of the following conditions as applicable:
    1. minimum current through TE input and maximum current through TE output;
    2. maximum current through TE input and maximum current through TE output; and
    3. maximum current through TE input and minimum current through TE output.

In cases where the interface impedances are not evident from the information provided, the tester shall contact the designer and request that this information be provided so that appropriate correction factors can be calculated for the throughtransmission loss measurements.

3.6.5.3 Alternative Method of Measurement

A discrete or sweptfrequency method may also be used.

Figure 3.6(d): Through Transmission (Digital) Measurement

Figure 3.6(d): Through Transmission (Digital) Measurement

[Description of Figure]

Notes:

  1. Select the appropriate loop simulator, holding circuit, or termination for the interface of the TE.
  2. Loop current is measured with a current meter in series with the loop simulator.
  3. The output impedance of the white noise source should be such that, in combination with or instead of the loop simulator circuit, the source impedance is either 600 ohms or matches the impedance of the circuit reference (see CS-03 Part 1).
  4. The zero level encoder/decoder of the loop simulator may be replaced with the equivalent impedance of the zero level encoder/decoder.
Figure 3.6(e): Arrangement for Figures 3.6(d) and (f)
Figure 3.6(e): Arrangement for Figures 3.6(d) and (f)

[Description of Figure]

3.6.5.4 Method of Measurement

Signal Frequency Guardbands

  1. Connect the digital TE with through ports embedded in the 1.544 Mbps system to the test circuits of Figures 3.6(e) and 3.6(f). Establish a connection between the ports under test.
  2. Set switch S1 to position "A."
  3. Set the generator to 800 Hz and adjust the output level to -11 dBV as measured by the spectrum analyzer.
  4. Set switch S1 to position "B" and measure the signal present at the output side of the TE.
  5. Calculate the gain at 800 Hz as the difference between the level set in step (3) and the level measured in step (4).
  6. Repeat steps (2) through (5) for frequencies of 1000, 2000, 2300 and 2600 Hz.
  7. Repeat steps (2) through (6) for each of the following conditions as applicable:
    1. minimum current through TE input and maximum current through TE output;
    2. maximum current through TE input and maximum current through TE output;
    3. maximum current through TE input and minimum current through TE output.
  8. If significant ripple is noticed (i.e. the change in gain over the frequency range is not smooth and monotonic), then, with switch S1 in position "A," sweep the frequency range from 800 Hz to 2400 Hz, noting the frequency at which the minimum value is indicated on the spectrum analyzer. Sweep the frequency band from 2450 Hz to 2750 Hz, noting the frequency at which the maximum value is indicated on the spectrum analyzer. Repeat steps (2) through (7) for these two frequencies with the minimum and maximum amplitude values.
  9. Repeat steps (2) through (8) for the opposite direction if applicable.

3.6.5.5 Alternative Method of Measurement

A method using a white noise source and two band pass filters may be used.

Figure 3.6(f): Through Transmission (Signal Frequency Guardbands, Digital)Measurement
Figure 3.6(f): Through Transmission (Signal Frequency Guardbands, Digital) Measurement

[Description of Figure]

Notes:

  1. Select the appropriate loop simulator, holding circuit, or termination for the interface of the TE.
  2. Loop current is measured with a current meter in series with the loop simulator.
  3. The output impedance of the frequency generator should be such that, in combination with or instead of the loop simulator circuit, the source impedance is either 600 ohms or matches the impedance of the circuit reference (see CS-03 Part I).
  4. The zero level encoder/decoder of the loop simulator may be replaced with the equivalent impedance of the zero level encoder/decoder.

3.6.6 Audio Signal Limiting

3.6.6.1 Signal Power Limiting Requirements

  1. When the TE provides a voice band through path from an external non-registered signal source, the requirements of Section 3.6.3 shall be met with an input level 10 dB above the overload point, but not exceeding 70 V rms (see note below).
  2. The TE shall have no user accessible adjustments that will allow these parameters to be exceeded.

Note: The overload point is determined as follows:

  1. for signal power limiting circuits incorporating the automatic gain control method, the overload point is the value of the input signal that is 15 dB greater than the capture level; and
  2. for signal power limiting circuits incorporating the peak limiting method, the overload point is defined as the input level at which the equipment's through gain decreases by 0.4 dB from its nominal constant gain.

3.6.6.2 Method of Measurement

  1. Connect a sine wave input of 1004 Hz to the audio input (audio input port) and monitor input and output (network interface) levels.
  2. Set the signal at a level at which through transmission gain is not significantly affected by moderate changes in level.
  3. Increase the input level until the through transmission gain has dropped by 0.4 dB or until 70 V rmsis reached, whichever input level is the lesser. The input level at which this occurs is defined as the overload point.

3.6.7 Automatic Dialling and Automatic Redialling

3.6.7.1 Requirements

Note: Emergency alarm diallers anddiallers under external computer control are exempt from these requirements.

  1. Automatic dialling to any individual number is limited to 2 successive attempts. Automatic dialling equipment which employs means for detecting both busy and reorder signals shall be permitted an additional 13 attempts if a busy or reorder signal is encountered on each attempt. The dialler shall be unable to reattempt a call to the same number for at least 60 minutes following either the second or fifteenth successive attempt, whichever applies, unless the dialler is reactivated by either manual or external means. This rule does not apply to manually activated diallers, which dial a number once following each activation.
  2. If means are employed for detecting both busy and reorder signals, the automatic dialling equipment shall return to its on-hook state within 15 seconds after detection of a busy or reorder signal.
  3. If the called party does not answer, the automatic dialler shall return to the on-hook state within 60 seconds of completion of dialling.
  4. If the called party answers and the calling equipment does not detect a compatible TE at the called end, the automatic dialling equipment shall be limited to one additional call which is answered. The automatic dialling equipment shall comply with (1), (2) and (3) for additional call attempts that are not answered.
  5. Sequential diallers shall dial only once to any individual number before proceeding to dial another number.
  6. Network addressing signals shall be transmitted no earlier than:
    1. 70 ms after receipt of dial tone at the network demarcation point;
    2. 600 ms after automatically going off-hook (for single line equipment that does not use dial tone detectors); or
    3. 70 ms after receipt of the central office (CO) ground-start at the network demarcation point.

3.6.7.2 Method of Measurement

No test method.

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