Thread Subject: Re: teitac-telecom, PSTN Reference

Note

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From: Gregg Vanderheiden
Date: Sat, Mar 31 2007 12:55 PM

See previous post.

We only need to talk about the public phone systems. (The PSTN and IP)

For other systems - we should treat them as proprietary and keep our hands
off until they meet with the public systems. At that time they would need
to be in the common public format.

There are too many non-public technologies and it would not be possible or
appropriate to specify what form they should use internally.



I think the Two Tier approach may be appropriate though.


A general guideline (that is testable)
- under it the specific testable guidelines where they are appropriate
- (sufficient techniques would not be in the guidelines but in support docs
from Access Board.


Gregg
-- ------------------------------
Gregg C Vanderheiden Ph.D.


> -----Original Message-----
> From: = EMAIL ADDRESS REMOVED = [mailto:teitac-telecom-
> = EMAIL ADDRESS REMOVED = ] On Behalf Of Jasionowski, Tony
> Sent: Monday, March 26, 2007 1:17 PM
> To: = EMAIL ADDRESS REMOVED =
> Subject: [teitac-telecom] teitac-telecom, PSTN Reference
>
> Paul,
> Noted, PSTN is also not acceptable for the reasons you passionately
> mention, therefore, I will investigate other suitable alternatives.
> Tony Jasionowski
> Panasonic
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 26 Mar 2007 09:28:09 -0600
> From: "Michaelis, Paul R. (Paul)" < = EMAIL ADDRESS REMOVED = >
> Subject: Re: [teitac-telecom] teitac-telecom, PSTN Reference
> To: "TEITAC Telecommunications Subcommittee"
> < = EMAIL ADDRESS REMOVED = >
> Message-ID:
>
> < = EMAIL ADDRESS REMOVED = >
>
> Content-Type: text/plain; charset="us-ascii"
>
> Tony,
>
> Quoting from the web page you cited:
>
> "Public Switched Telephone Network communications (PSTN, T.70) The
> collection of interconnected systems operated by the various telephone
> companies and administrations (telcos and PTTs) around the world. Also
> known as the Plain Old Telephone System (POTS) in contrast to xDSL and
> ISDN (not to mention other forms of PANS)."
>
> Note that this definition seems to say that services such as ISDN are
> *not* considered to be PSTN. Presumably, this would also mean that
> digital telephones, operating behind a PBX, are not PSTN. These phones
> are not IP either. This would mean that the proposal to classify
> equipment as either PSTN or IP will leave an entire category of telecom
> equipment without an obvious home.
>
> A reason why I am passionate about this issue is that I've wasted a
> tremendous amount of time over the past seven years, arguing with people
> -- including people in my own company -- about how to interpret the
> Section 508 requirements. "This requirement means this!" "No, it means
> that!!!" As part of the Section 508 refresh, we need to write
> unambiguous requirements that cannot be misinterpreted. Without that,
> contract officers will continue to buy whatever the heck they want,
> manufacturers will continue to sell inaccessible solutions to the
> government, and the likelihood that my company will let me build
> anything else will be close to nil.
>
> Getting back to the use of "PSTN" to describe non-IP phones, my fear is
> that some people who are looking for an excuse to avoid investing in
> accessibility -- including people in my own company -- will claim that
> ISDN and digital phones behind a PBX are exempt because they don't fall
> into either category. During the next seven years, I want to spend more
> time building solutions, and less time arguing about whether they ought
> to be built.
>
> -- Paul Michaelis
>
>
>
>
> -----Original Message-----
> From: Jasionowski, Tony [mailto: = EMAIL ADDRESS REMOVED = ]
> Sent: Monday, March 26, 2007 7:42 AM
> To: = EMAIL ADDRESS REMOVED =
> Subject: [teitac-telecom] teitac-telecom, PSTN Reference
>
> Paul,
> "wired analog and wired non-IP digital" seems odd considering we also
> have "cordless analog and digital". I suggest we stick with PSTN for now
> unless someone can propose acceptable alternative term. FYI, anyone can
> easily find the definition of PSTN at several web sites including:
> http://dictionary.reference.com/browse/pstn
> Therefore, PSTN may not be so confusing after all.
> Tony Jasionowski
> Panasonic
>
>
> Message: 1
> Date: Sat, 24 Mar 2007 17:41:44 -0600
> From: "Michaelis, Paul R. (Paul)" < = EMAIL ADDRESS REMOVED = >
> Subject: Re: [teitac-telecom] Telecommunications Working Group- Draft
> 1 Template for 508 in WORD
> To: "TEITAC Telecommunications Subcommittee"
> < = EMAIL ADDRESS REMOVED = >
> Cc: = EMAIL ADDRESS REMOVED = , Creagan Tim
> < = EMAIL ADDRESS REMOVED = >
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>
> < = EMAIL ADDRESS REMOVED = >
>
> Content-Type: text/plain; charset="us-ascii"
>
> Regarding the reference to "PSTN" versus "IP" in many of the proposed
> requirements, I agree that IP telephones should be treated differently
> but am concerned that describing the non-IP systems as "PSTN" will
> create a lot of confusion.
>
>
>
> The "PSTN" is the Public Switched Telephone Network. If asked to
> describe a PSTN telephony endpoint, I imagine that most telecom
> specialists would say it was an analog device that complies with the FCC
> regulations that govern residential telephones. If we use this
> definition, I can't remember the last time I've seen a government
> procurement of telecom equipment that falls into this category.
>
>
>
> There are at least three different categories of non-IP wired telephones
> in common use today:
>
>
>
> Residential analog. (This is what most folks would classify as a "PSTN
> phone.")
>
>
>
> Enterprise analog. (The distinction between these phones and
> residential analog sets is that the enterprise sets connect to the PSTN
> via a PBX or switch that is owned by the enterprise. An important
> electrical distinction is that, unlike enterprise analog telephones,
> residential telephones are required to do "automatic loop length
> compensation" to account for distance-related differences in electrical
> resistance and capacitance in the line between the phone and the
> associated central office. Another important distinction is that many
> enterprise analog solutions are actually hybrid analog/digital sets.
> The audio stream is carried as traditional analog, supplemented by
> digital signaling that, for example, controls the phone's display.)
>
>
>
> Enterprise digital. (This is what is purchased in the vast majority of
> non-IP wired telephony procurements by the government. All audio
> transmissions entering or leaving the phone are digitally encoded,
> typically using the G.711 algorithm that I described in a previous
> message. Signaling and call control is also digital, typically using
> protocols that are proprietary to the individual manufacturers.)
>
>
>
> Wired residential analog systems, wired enterprise analog systems, and
> wired enterprise digital systems are able to transmit Baudot TTY signals
> with 100% reliability. IP telephony is different.
>
>
>
> Depending on network characteristics, the mechanisms that are used in
> order to transport voice signals within IP networks are not always
> suitable for transporting Baudot TTY tones. Common sources of
> impairment include packet loss and the use of voice-optimized audio
> compression algorithms, such as G.729. For this reason, a traditional
> TTY device used in conjunction with an IP phone (for example, via an
> acoustic coupler) is not always going to be reliable.
>
>
>
> The good news is that, although not yet in common use, there are
> international standards that describe how to transport text and Baudot
> tones reliably on IP networks. In general, these techniques do not use
> the same audio encoding and transmission mechanisms that are used for
> voice. I agree completely that the availability of these techniques,
> coupled with the inherent unreliability of Baudot TTY transmissions via
> the "voice channels" of IP telephone networks, makes it essential that
> we treat IP telephony as a special case in the Section 508 refresh.
>
>
>
> Getting back to the original topic of my message... We need a term
> other than PSTN to describe non-IP wired telephony. Ideally, it should
> be a term or description that would make sense to someone who is not
> knowledgeable about telephone engineering. To start the ball rolling, I
> suggest "wired analog and wired non-IP digital" as a substitute for
> PSTN. (I deliberately use the word "wired" because wireless devices
> have special characteristics that may need to be addressed separately.)
>
>
>
> -- Paul Michaelis
>
>
>
>
>
>
>

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