Meeting Notes for TR-41.3.5 Interim Web Conference on January 16, 2013
The TR-41.3.5 Working Group held an interim web conference on Wednesday, January 16, 2013. Chair Steve Whitesell called the meeting to order at 1:05 PM EST. Those in attendance at the meeting are shown below.
Steve reviewed the TIA Important Notice of Participation regarding participation in the meeting being bound by provisions of the TIA Engineering Manual. He also reviewed the TIA Intellectual Property Rights Policy as described in the Engineering Manual. He asked if anyone was aware of patents or published pending patent applications that were essential to the practice of the standards being developed. None were identified.
The purpose of the meeting was to review Draft 0.2 of the ANSI/TIA-PN-470.112 standard on wideband analog telephones with handsets as found in contribution TR41.3.5-13-02-006. Since he is also serving as editor of the document, Chair Steve Whitesell created an R1 version of the document to capture comments and revisions made during the meeting to become Draft 0.3. Contribution TR-41.3.5-13-02-010 from Tim Lawler of Cisco, providing comments on some Conversational Gain measurements he had made, was also considered.
During discussion of the Scope, Dean Morgan of Microsemi questioned whether the wideband frequency upper band edge should be specified as 7000 Hz as now shown in the document of as 6800 Hz as specified in Cable Labs documents. The use of 7000 Hz is consistent with the TIA-920.110-A wideband digital standard, but the Chair will consultant ITU-T and other sources to determine which frequency should be specified.
In reviewing the changes made to the list of Acronyms in Clause 3.1, Steve Whitesell raised an issue about whether CPE (Customer Premises Equipment) should be retained. He pointed out the term is typically used in TR-41 standards to refer to the Equipment Under Test (EUT). However, both the wideband telephone that is the subject of this standard and the terminal adapter or gateway device to which it is connected are both CPE, and it is only the former that is the EUT. The decision was made to retain the term but to exercise care in how it is used.
The question of whether the CPE load simulator described in 4.2.6 and the parallel set off-hook send and receive tests should be retained. Steve indicated he had already decided to remove the somewhat related conference mode send and receive tests pending someone speaking up to say they should be retained. No one on the call expressed a viewpoint. Steve made a note to contact James Bress, who had to cancel participation on the call due to a conflict, about this issue since it was thought he might have an opinion.
Steve indicated he had tentatively deleted the requirement in step 3 of 220.127.116.11.3 for the handset to be in the HATS position when measuring send single frequency interference. He noted there was no corresponding requirement in the related send noise test procedure, and that he didn’t see a real need for it. However, it was thought this was another item on which Jim Bress might have experience or an opinion, so Steve took a note to check with him about it.
Dean Morgan raised a couple of questions about the frequencies selected for the send distortion (SDNR) tests in Clause 5.2.4. One was why the highest frequency used for testing was only 2500 Hz for a wideband telephone. Steve explained that he had copied the test conditions for the wideband digital standard TIA-920.110-A and that he believed the reason had to do with picking a frequency that would have harmonic content in the measurement band. The other question was why 800 Hz was used for the measurements across input levels instead of 1000 of 1004 Hz, which is evidently used for some codecs. Steve agreed to ask IEEE STIT Chair John Bareham about both questions since the frequencies used are those recommended in IEEE Std 269-2010.
Steve noted that he had specified a 600-ohm loaded signal level of -30 dBV to be used for receive tests, which are made under zero loop conditions. He indicated he believed this to be consistent with the -28 dBm mean far end Active Speech Level (ASL) cited in Bellcore SR-2476, Annex B and equivalent to the 25 dBV level with an average 2.7 km loop specified for speakerphone testing in TIA-470.120-C. Tim Lawler’s contribution TR41.3.5-13-02-010 discusses some measurements he made on Conversational Gain where he confirmed that a -25 dBV signal into a 2.7 km loop resulted in -29.7 dBV at the line terminals of the EUT. Steve made a note to consult with Jim Bress about this relationship and the use of -30dBV as the normal test level.
A discussion ensued about the specification of 2 dB for the nominal RLR value. This is consistent with the nominal requirements in TIA-920.110-A for digital telephones, in ETSI EN 300 175-8 for DECT telephones, and the overall transmission plan requirements in ITU-T Recommendation G.101. However, that value assumes 0 dB loss in the receive direction of the gateway or terminal adapter to which the phone is connected. Dean Morgan said he thought this was probably not the case and agreed to provide a contribution providing information from Cable Labs and Telcordia document on this subject. Tim Lawler was asked to provide a similar contribution about the loss plan for Cisco products. It was noted that the narrowband analog telephone nominal RLR value is -3dB based on an assumption of 6 dB loss in the PSTN end office and in gateways (covered by TIA-912-B) and PBXs (covered by TIA-464-C-1).
The test method for Conversational Gain calls for using the same 600 ohm source set up with no loop as for all other receive tests. Tim Lawler pointed out in his TR41.3.5-13-02-010 contribution that the phone would also have to be tested to ANSI/TIA-4965 (assuming this standard is adopted by the FCC) for showing receive volume control compliance for Part 68. In that case, it will have to be tested using a 900 ohm source with a 2.7 km loop and a -25 dBV signal. The results should be approximately the same. Should we delete the test method from the wideband standard and simply require compliance with ANSI/TIA-4965? Should 4965 be revised to include requirements for wideband telephones?
Steve noted that the term Reference Volume Control Setting needed to be changed to Nominal Volume Control Setting wherever it occurs in the document. He will do a search and take care of this.
Clause 5.6 covers magnetic field requirements for hearing aid coupling. At present, the draft calls for compliance with ANSI/TIA-1083-A. Linda Kozma-Spytek has noted our work on the wideband standard and asked if we are going to include wideband magnetic coupling requirements. Steve indicated his discussion with her suggested it might be better to revise ANSI/TIA-1083-A to add wideband performance requirements rather than putting them into individual wideband documents like ANSI/TIA-470.112. It already includes a test procedure using the wideband L16-256 codec, but the performance requirements are only specified up to 3300 Hz.
The question of whether to keep the Loss Plan and Loudness Rating diagram in Annex D was discussed. It was this discussion that led to the question about whether RLR = 2 dB is the correct nominal value for wideband Analog telephones as discussed above. It may be a good idea to update the diagram to include TIA-470.112 and retain it.
Input is also sought on whether the Annex E list of other parameters that may influence product performance should be retained.
The meeting was adjourned at approximately 2:45 PM EST