Telecommunications Industry Association
TR41.9-11-08-007
Document Cover Sheet
Project Number
Document Title
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Contact
Al Baum
Uniden American Corporation
Distribution
TR-41.9
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of Document
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Phone: (817) 858-3624
Fax:
Email: abaum@uniden.com
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The document to which this cover statement is attached is submitted to a Formulating Group or
sub-element thereof of the Telecommunications Industry Association (TIA) in accordance with the
provisions of Sections 6.4.1–6.4.6 inclusive of the TIA Engineering Manual dated October 2009, all
of which provisions are hereby incorporated by reference.
Abstract
Explanation of low leak position
The Canadian and US regulations specify measuring ROLR per ANSI/EIA/TIA–579–1991 which in turn
specifies the measurement method in IEEE 269-1991 Section 7.4 (it should have said -1992). IEEE 2691992 Section 5.4 specifies the use of an IEC-318 coupler for supra-aural earphones and points to CCITT
P.51 for possible modification of the coupler for particular ear-cap configurations. In practice just about
everyone used the IEC-318 for all ear-cap configurations and added sealing putty if the ear-cap didn’t
naturally seal to the coupler. Therefore manufacturers designed their phones for a sealed condition
(whether or not a seal was in fact obtainable during actual use).
Around the turn of the century (circa 2000) the IEEE Subcommittee on Telephone Instrument Testing
(STIT) (the formulating group that writes/maintains IEEE Std 269) encouraged TIA TR-41 to revise our
CPE performance standards to use the Head and Torso Simulator (HATS) for transmission
measurements. It quickly became clear that this was the correct way to measure receive acoustic
performance for a broad range of receiver types and that it more accurately simulated the leaky condition
experienced during actual use of the telephone. However, TR-41 writes voluntary standards and
recognized that there would be disincentives for manufacturers and test labs to switch from the IEC-318
to the HATS. First of all, this change would require manufacturers and test labs to purchase a HATS at a
cost of about $30K each. Secondly, most phones in the market at that time were designed to pass the
TIA frequency response and loudness rating requirements in a sealed condition using the ITU-T Type 1
ear simulator (a.k.a. IEC-318 coupler) but now these same phones suddenly had a haystack receive
response and quieter loudness ratings when tested with a HATS. Switching to the HATS resulted in
“good” phones becoming “bad” phones overnight.
Telecommunications Industry Association
TR41.9-11-08-007
To overcome these disincentives we considered allowing the use of either the IEC-318 or the HATS but in
such a case it was believed that most companies would simply ignore the HATS and continue to use the
Type 1 ear simulator with putty (even if we prohibited the use of putty in the standard). Therefore, we
decided to require the use of the HATS in the High Leak position for most tests to better represent real
use performance but we also included a Low Leak position that was intended to approximate the IEC-318
(as much as is possible with a Type 3.3 pinna) for a couple of tests that were intended to be equivalent to
the regulatory HAC Volume Control tests. In the Low Leak position, the measured RLR values were
louder than in the High Leak position, approaching the equivalent ROLR values obtained with the IEC318 coupler. If the government regulations were revised to specify using the HATS at the High Leak
position but continue to specify the old ROLR limits (or their RLR equivalents) this would represent an
actual requirement change in addition to the measurement method change and require at least some
telephone manufacturers to add more amplification to their products in order to meet the baseline
(unamplified) loudness rating requirement in the High Leak position.
As a means to prevent “good” phones from becoming “bad” phones overnight, we included a wide open
“Mandatory” receive response mask and a quieter “Mandatory” minimum RLR requirement for the High
Leak position in addition to a narrower more traditional “Desired” receive response mask and “Desired”
RLR requirement for the High Leak position. However, from the beginning our intent was for this
loosening of the requirements to be temporary and transitional. Future revisions of the standards would
delete the wide open receive frequency response mask and lower minimum RLR requirement leaving the
traditional response mask and RLR requirement as the only requirement for the High Leak position. This
revision process has started. TIA-470.110-D-Draft has deleted the wide receive response mask and
furthermore it now specifies that ALL testing be done at the High Leak position only.
It should be noted that TIA TSB-31-D “Rationale and Measurement Guidelines for U.S. Network
Protection” was just approved by TIA TR-41.9. In Clause 14.2 “Hearing Aid Compatibility - Volume
Control 47 C.F.R., 68.317” it specifies measuring RLR using a HATS in the High Leak position and using
a formula to convert the measured RLR to ROLR for comparison with the FCC ROLR requirements.
Then it says: “Alternatively, the handset receiver may be placed on artificial ear SEL#51 if a seal can be
achieved between the handset surface and the rim of the artificial ear without the use of sealing putty or
similar materials.” (SEL#51 is an IEC-318 coupler.) It should be kept in mind that TSB-31-D is not a
standard but a Telecommunications Systems Bulletin. As it says in its Foreward: “Telecommunications
Systems Bulletins are distinguished from TIA Standards in that TSBs contain a compilation of engineering
data or information useful to the technical community and represent approaches to good engineering
practices suggested by formulating group TR-41.9.”
This has been copied to Steve Whitesell the Chair of TR-41 and James Bress the Vice-Chair of TR-41.3
and I welcome any corrections, clarifications, or other comments that they might desire to provide on this
subject.
Now for my opinion.
I would rather see Industry Canada and the FCC revise their HAC Volume Control regulations to specify
the requirement in terms of the new “Conversational Gain” metric. By way of background, I have
attached a copy of the TIA submission I wrote in 2008 on the subject and also a PowerPoint presentation
from a TIA Workshop I co-presented at the HLAA National Convention in Washington D.C. last month.
(My part of the presentation begins on slide 24.) Last year, in the TIA/CTIA joint reply comments to the
U.S. Access Board’s Advanced NPRM they stated “TIA/CTIA recommend that Conversational Gain be
considered as the method of measurement for volume gain for Wireline devices.”
Telecommunications Industry Association
Best regards,
Al Baum
Chair, TIA TR-41.3
Uniden America Corporation
Phone: (817) 858-3624
Email: abaum@uniden.com
TR41.9-11-08-007
Telecommunications Industry Association
TR41.9-11-08-007
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