Download TSB31-B Errata - Telecommunications Industry Association

TR41.1-04-xx-xxx
Title: Comments on proposed draft for “Analog Telephone Port
Requirements for VoIP Terminal Adapters,” TR-41-04-08006.
Distribution to: TIA TR41.1
Meeting Location: San Antonio, Texas
11 November, 2004
Submitting Infineon Technologies
Organization:
Contact
Information:
Christian Mitterschiffthaler
Infineon Technologies
Siemensstrasse 2
Villach 9500
AUSTRIA
Phone +43 4242-305-6020
Fax +43 4242-305-6260
Email
Neal J. King
Infineon Technologies
Balanstrasse 73
Munich 81541
GERMANY
Phone: +49 160-9064-3593
Fax
+49 89-234-955-9870
Email [email protected]
[email protected]
Keywords: Packet Based, Analog Telephone Port, VoIP, Terminal Adapter
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This document has been prepared by Infineon Technologies 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 Infineon
Technologies. Infineon Technologies 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 Infineon Technologies other than provided in the copyright statement above.
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TR41.1-04-xx-xxx
Introduction
Infineon Technologies appreciates the hard work and expertise that has gone into the text
proposal by Siemens ICN for the draft of “Analog Telephone Port Requirements for VoIP
Terminal Adapters,” TR-41-04-08-006. However, on careful reading, we have come across some
points for which we feel that further clarification would be helpful. We also think there are some
changes that might broaden the scope of the market to which the specification is addressed.
These are detailed below.
It is also possible that we will come across further points of interest in our continued study of the
draft.
Detailed Comments
5.1.1.4
The requirements in this section are intended to assure acceptable performance provided the
manufacturer's specified limitations are observed. The parameter (N) of the analog telephone port shall be a
minimum of 5 to ensure that any FCC-certified analog telephony equipment with which the VoIP analog terminal
adapter is compatible can be connected to the analog telephone port.
Comment:
We question the need to require a minimum of 5 REN for the VoIP analog terminal adapter. This
high a value will have severe implications for the complexity of the implementation. Is this really
justified in terms of the relevant deployment scenarios for VoIP phones, either in terms of
numbers of phones or in terms of the types of phones? Perhaps the N parameter should be a point
of differentiation among vendors.
5.1.3.1
Battery voltages applied by the VoIP analog telephone port to the tip and ring (T&R) leads for
supervisory purposes shall not exceed 56.5 Vdc and shall have no ac component in excess of 5 V peak.
Comment:
We don’t understand why the voltage applied by the battery should have any AC component.
Does this refer to a signal used for on-hook transmission?
5.1.3.2
The characteristic of the dc battery source applied by the VoIP analog telephone port to the T&R leads
shall result in a loop current within the range of 20 to 140 mA being delivered into a load connected across the
interface leads, having a load resistance that falls within the combined acceptable regions A and B shown in Figure 2
(normal power available) or Figure 3 (commercial power outage) if backup power is provided to the VoIP analog
terminal adapter. It is desirable that the voltage-versus-current function, V(I), at the interface falls in the combined
acceptable region A shown in Figures 2 or 3. This requirement applies throughout the full loop resistance range (R)
specified for the VoIP analog terminal adapter by the manufacturer.
Comment:
These figures seem to specify the load. Wouldn’t it be better to specify the voltage vs. current for
the feeding side? For example, a minimum current of 20 mA for a load of minimum full-loop
resistance range R + reserve. The short-cut current must not exceed 140 mA. Our proposal is in
Figure 2 below:
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TR41.1-04-xx-xxx
Figure 2: Proposed definition for Voltage-vs.-Current (fine red lines)
5.1.3.3
It is desirable that the battery voltage source supplied by the VoIP analog telephone port delivers between
36 and 63 mA into a 130  resistive load connected across the analog telephone port T&R leads. This is typically
accomplished with a 42.5 to 56.5 V, 800  source or a 21 to 29 V, 400  source.
Comment:
The upper limit for the current seems much higher than should be necessary, in our judgement.
This would lead to excessive power dissipation, temperature requirements, and packaging size. In
any case, wouldn’t these specifications overlap (and possibly conflict) with the voltage vs.
current function specified in Section 5.1.3.2?
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TR41.1-04-xx-xxx
5.1.3.4 It is desirable that the battery voltage supplied to the VoIP analog telephone port be negative with respect
to ground.
Comment:
This seems to be an issue relevant for outside cabling: See, for example, GR-1089:
8 Corrosion
8.1
Polarity of DC Voltages Applied to Outside Plant Cabling
O8-1 [72] It is desirable that equipment ports which interface with the outside plant
should apply only DC voltages which are zero or negative in polarity with respect to
ground to minimize stray current corrosion in outside plant cables and equipment where
water intrusion may occur.
Is it really necessary for this point to be included in this specification? Is there always a ground
connection for CPE equipment? For example, Ethernet ports usually don’t have a ground
reference, nor does the AC power supply.
5.1.4.1
The VoIP analog telephone port ringing shall comply with Table 1.
Table 1 - Ringing Voltage Ranges and Terminating Impedances
Ringing Frequency (Hz)
Terminating Impedance ()
Ringing Voltage (V rms)
17 – 23
10,000/(N)
55 - 130
20
8,000/(N)
40 - 130
27 – 33
10,000/(N)
95 - 130
Where (N) = the number of station ringer equivalence with which the VoIP analog telephone port
is designed to work.
Comment:
The requirement of 95 Vrms seems much too high. For example, the Telcordia GR-57 requires
only 40 Vrms at the end of the line to support 5 REN.
5.1.4.2
It is desirable that the ringing voltage be within the range 75 to 100 V rms.
Comment:
For short loops, 75 Vrms seems too high, and reducing this value, for example, to 60 Vrms,
would result in lesser power consumption and lower complexity.
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TR41.1-04-xx-xxx
5.1.4.3
Each VoIP analog telephone port shall support 5 REN
Comment:
We believe that a better approach would be to make a value of 3 REN mandatory and 5 REN
optional.
5.1.5.3
The magnitude of each signal is approximately 20 to 45 Vrms from each conductor to ground. The dc offset
between conductors may be in the range of approximately 0 to 25 V. The dc offset between conductors and ground
may be in the range of approximately 0 to 25 V positive or negative respective to ground.
Comment:
a) Hasn’t the magnitude of the ringing voltage already been defined in Section 5.1.4?
b) We are in agreement on the range for the DC offset between conductors.
c) We do not see the need for restricting the DC offset to ground. To provide unbalanced
ringing, there is a DC offset from Ring to ground of typically -48 V, from the battery. We
believe that the maximum DC battery voltage should be allowed, in this case 56.5 V.
5.1.7 Ringing Pre-trip.
To assure adequate protection against false ringing trip, the VoIP terminal adapter analog telephone port
ringing trip circuit shall not trip ringing when tested under the following conditions:
(1)
A terminating impedance simulating on-hook impedance, connected across the telephone line
conductors and composed of the parallel combination of 15 k resistance and a series
connection of resistance and capacitance whose impedance at the specified frequency is as
shown in Table 2.
(2)
A loop resistance range between the VoIP terminal adapter analog telephone port and the
terminating impedance equal to the specified analog telephone working loop resistance of the
VoIP analog terminal adapter.
Comment:
We do not understand point (2). Is it a specification for the resistance at which the circuit must
detect ring-trip? Our view would be that the circuit must detect ring-trip if the termination
impedance is in the range of the specified analog telephone working-loop resistance. Is this in
agreement?
5.1.9.2
When the analog telephone port is in the idle state (on-hook), it is desirable that spurious off-hook signals
of 150 ms or less be ignored to prevent false seizures.
Comment:
150 ms seems like a very long time. What is the source of this requirement?
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5.1.12.1 The VoIP analog terminal adapter shall alert analog telephony equipment by applying ringing, as described
in 5.1.3, across the analog telephone port tip-and-ring conductors with the tip conductor effectively at ground
potential.
Comment:
The ringing behavior has already been specified in Sections 5.1.4 through 5.1.7.
Doesn’t the statement that the tip conductor is effectively at ground in contradiction to Section
5.1.5, on balanced ringing?
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