Download 1 - Telecommunications Industry Association

Proposed change/modification
Document Number: TR-41.9.2-04-02-013-R1
Document Number: TR-41.9.2-02-11-010
STANDARDS PROJECT:
TR41.9.2 - TSB31-C, Section 9.16 Non-LADC Metallic Voltage - 4 kHz to
30 MHz updates
TITLE:
Proposal to revise TSB31-C, Section 9.16 Non-LADC Metallic Voltage 4 kHz to 30 MHz test procedures
ISSUES ADDRESSED:
Update TSB31-C, Section 9.16. Added to the comments test method for
TIA-968-A, sections 4.5.7.3 (Through Transmission from Other
Equipment) and 4.5.7.4 (Music on Hold, Out Of Band).
SOURCE:
Cisco Systems
CONTACTS:
Tim Lawler, Cisco Systems, e-mail: [email protected]
DATE:
February 24, 2004
DISTRIBUTION TO:
TIA TR-41.9.2 (TSB-31-C working group)
KEYWORDS:
TIA-968-A Non-LADC Metallic Voltage - 4 kHz to 30 MHz test
procedures
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This document has been prepared by Cisco Systems to assist the TIA Engineering Committee. It is
proposed to the Committee as a basis for discussion and is not to be construed as a binding proposal on
Cisco Systems. Cisco Systems specifically reserves the right to amend or modify the material contained
herein and nothing herein shall be construed as conferring or offering licenses or rights with respect to
any intellectual property of Cisco Systems other than provided in the copyright statement above.
9.16
Non-LADC Metallic Voltage - 4 kHz to 30 MHz TIA-968-A, 4.5.5.1
9.16.1
Background
This requirement ensures that spurious or unintended signals transmitted from terminal
equipment at frequencies above voiceband do not interfere with telephone company
transmission systems or services that function at such frequencies. The most limiting situations
are those that involve subscriber multichannel analog carrier systems. These are systems that
are used in the local exchange plant to obtain a wire pair gain advantage. In these systems, the
signals to and from several subscribers are multiplexed onto a wire pair using frequency
division. Each direction of transmission for each subscriber uses either 4 kHz (single sideband)
or 8 kHz (double sideband) of frequency spectrum. Generally, the carrier systems most
susceptible to crosstalk are those that use double sideband modulation methods, 8 kHz of
spectrum for each direction of transmission per channel.
Accordingly, the requirements in TIA-968-A are specified in 8 kHz bands relative to the center
frequency of each band. Thus the limits in each band are based on the susceptibility of the
affected analog multichannel carrier system, crosstalk characteristics of the wire pair cable
facilities, and the characteristic terminating impedance of the cable facilities. The limit is
therefore established for each 8 kHz band centered in the frequency specified in the tables up to
270 kHz.
The 100-millisecond averaging time for frequencies less than 270 kHz approximates the
minimum time necessary for the interfering signal to affect the transmission performance of
subscriber analog carrier systems on other cable pairs. For frequencies greater than 270 kHz, a
2-microsecond averaging time is specified. This averaging time is approximately the reciprocal
of the Nyquist rate of "T" carrier. It represents the time interval appropriate to interference with
the "T" carrier transmission. Such a signal duration will result in pulse interference and
consequently transmission errors. One broadband requirement above 270 kHz is adequate.
9.16.2
Purpose
To verify that the EUT does not apply excessive out-of-band power to the PSTN.
9.16.3
Equipment
(1)
Applicable loop simulator SEL# 4.
(2)
Bandpass filter SEL# 9
(3)
Digital sampling storage oscilloscope SEL# 24.
(4)
Spectrum analyzer SEL# 34
(5)
Frequency Generator SEL# 27
NOTE: Refer to Section 4.3 for equipment details.
9.16.4
Equipment States Subject to Test
(1)
On-hook.
(2)
All active operating states.
9.16.5
Procedure
NOTE: See comments (1), (2), (3) and (6) before performing tests.
(1)
Connect the EUT to the test circuit of Figure 9.16-1.
(2)
Place the EUT in the on-hook state.
(3)
Select R1 to be 300 ohms.
(4)
Measure the energy in each 8 kHz band whose center frequency is in the range of 8
kHz to 12 kHz, and record the results.
(5)
Select R1 to be 135 ohms.
(6)
Measure the energy in each 8 kHz band whose center frequency is in the range of 12
kHz to 90 kHz, and record the results.
(7)
Measure the energy in each 8 kHz band whose center frequency is in the range of 90
kHz to 266 kHz and record the worst case result.
(8)
Place the EUT in each of its off-hook states as specified in TIA-968-A Section
4.5.7.2, and condition the EUT as specified in TIA-968-A Section 4.5.7.3 or 4.5.7.4,
as appropriate (see comment 7 and 8).
(9)
Repeat step (3) through step (7) at minimum and maximum loop currents attainable
with the loop simulator, if applicable.
(10) Connect the EUT to the test circuit of Figure 9.16-2, and set the passband of the filter
to measure broadband energy in the frequency range 270 kHz to 30 MHz (see
comment 4 and 5).
(11) Condition the EUT to the on-hook state.
(12) Set the digital oscilloscope to provide:
(a)
2 µs per sample;
(b)
Trigger at -25 dBV;
(c)
Accumulate mode;
(d)
Vertical scale 0 mV to 250 mV full height.
NOTE: If the baseline contains 1000 points then a single trace will take 2 ms.
(13) Program the oscilloscope to accumulate 10 traces.
(14) Record the value of the largest peak measured and convert to V rms by multiplying
by 0.707.
(15) With the EUT in each of its active operating states as specified in TIA-968-A Section
4.5.7.2, condition the EUT as specified in TIA-968-A Section 4.5.7.3 or 4.5.7.4, as
appropriate (see comment 7 and 8).
(16) Repeat step (13) and step (14) at minimum and maximum loop currents attainable
with the loop simulator, if applicable.
9.16.6
Alternative Method - Broadband Procedure
NOTE: See comments (2), (3), and (5).
(1)
Connect the EUT to the test circuit of Figure 9.16-1.
(2)
Place the EUT in the on-hook state.
(3)
Select R1 to be 300 ohms.
(4)
Set the spectrum analyzer to measure broadband energy in the frequency range 4
kHz to 16 kHz, using the required termination, and record the result.
(5)
Select R1 to be 135 ohms.
(6)
Set the spectrum analyzer to measure broadband energy in the frequency range 8
kHz to 94 kHz, and record the result.
(7)
Set the spectrum analyzer to measure broadband energy in the frequency range 86
kHz to 270 kHz, and record the worst case result.
(8)
Set the spectrum analyzer to measure broadband energy in the frequency range 270
kHz to 6 MHz, and record the worst case result.
(9)
Set the spectrum analyzer to measure broadband energy in the frequency range 6
MHz to 30 MHz, and record the worst case result.
(10) Place the EUT in each of its off-hook states as specified in TIA-968-A Section
4.5.7.2, and condition the EUT as specified in TIA-968 Section 4.5.7.3 or 4.5.7.4, as
appropriate (see comment 7 and 8).
(11) Repeat step (3) through step (9) at minimum and maximum loop currents attainable
with the loop simulator, if applicable.
(12) If the test results obtained in step (4) and step (6) through step (9) do not exceed the
maximum limits specified in TIA-968 Section 4.5.5.1, then no further tests are
required (see comment 2).
9.16.7
Suggested Test Data
(1)
Center frequencies.
(2)
Start and stop frequencies.
(3)
Measured or calculated signal power values.
(4)
Equipment state.
9.16.8
Comments
When using a detector that measures individual frequency components, the following
procedure should be employed.
(1)
Total the voltages which are within 6 dB of the specified limit in each consecutive
band. If the sum of these voltages exceeds the limits, recheck the measurement at a
frequency centered over the band with the apparent failure.
The total rms voltage can be calculated using the expression:
Vt = (V12 + V22 + . . . + Vn2 )0.5
NOTE: This expression assumes that the spectral components have random
phase relationships.
(2)
The broadband measurement procedure may be used for the purpose of economy of
measurement. If the value obtained is lower than the most restrictive limit specified
for that frequency range, then the signal levels in 8 kHz bands in that range will be
lower than that specified for the most restrictive 8 kHz band. However, the main
procedure of Section 9.16.5 should be used when the requirements are not met as
the signal levels in each band may still be within specified limits. Refer to TIA-968-A
Section 4.5.5.1.
(3)
If a spectrum analyzer is used and it does not have an 8 kHz bandwidth, a 10 kHz
bandwidth may be used. Application of a correction factor, additional measurements,
or both, may be required to compensate for the wider bandwidth.
(4)
If a failure condition is noted when a 10 kHz bandwidth is used and the spectral
content has uneven distribution, it may be necessary to check that reading, using a
higher resolution.
(5)
The total rms voltage over an 8 kHz band can be calculated using the expression:
Vt = (V12 + V22 + . . . + Vn2 )0.5
where Vt is the total rms voltage over any 8 kHz band and V1, V2, V3....Vn are the
spectral components within that band that are within 20 dB of the limit for the band
in question.
NOTE: This expression assumes that the spectral components have random
phase relationships.
If the spectral content of a band is evenly distributed, then the equivalent rms
power in an 8 kHz band can be found by subtracting 1 dB from the measured
power using a 10 kHz bandwidth.
Since this is a measurement of a metallic (balanced) circuit, the only ground
connection should be that of the line cord of the oscilloscope or spectrum analyzer.
(6)
See TIA-968-A Section 4.5.7.2 through 4.5.7.4 for the conditions that apply for
different equipment types.
(7)
For approved terminal equipment or protective circuits with provision for throughtransmission from other equipment, apply a 1000 Hz signal from a 600 ohm source
that results in a power output of -13 dBm delivered into a 600 ohm load at the
network interface.
(8)
The EUT input test levels and frequencies that should be used in testing protective
circuits for compliance with all out-of-band frequencies are as follows:
(a)
For approved data protective circuits, apply a 1000 Hz signal that is 10 dB
higher then the overload point as determined in Section x.x.
(b)
For approved terminal equipment or approved protective circuits with nonapproved signal source input, such as music on hold, apply a swept sinusoidal
signal with a frequency range of 200 Hz to 20 kHz and the level set at the
overload point determined in Section x.x.
NOTES:
(1)
Select the appropriate loop simulator for the interface of the EUT.
(2)
Loop current is measured with a current meter in series with R2 of the loop simulator.
Refer to the figures of Section 1 of TIA-968-A.
(3)
The resistor shown (R1) is connected in place of R1 as shown in the loop simulator
drawing. The resistor has a value of 300 Ohms for frequencies of 4 kHz to 12 kHz
and 135 Ohms for frequencies of 12 kHz to 30 MHz. Capacitor C1 of the loop
simulator should be capable of coupling the frequencies covered by this test.
(4)
The spectrum analyzer should provide a balanced input, or an isolation transformer
or balun transformer may be used.
FIGURE 9.16-1. NON-LADC METALLIC 4 KHZ TO 30 MHZ
NOTES:
(1)
Select the appropriate loop simulator for the interface of the EUT.
(2)
Loop current is measured with a current meter in series with R2 of the loop simulator.
Refer to the figures of Section 1 of TIA-968-A.
(3)
The resistor shown (R1) is connected in place of R1 as shown in the loop simulator
drawing. The resistor has a value of 135 Ohms. Capacitor C1 of the loop simulator
should be capable of coupling the frequencies covered by this test.
(4)
The oscilloscope should provide a balanced input, or an isolation transformer or
balun transformer may be used.
FIGURE 9.16-2. NON-LADC METALLIC 270 KHZ TO 30 MHZ