Telephonic communications – Including aid for handicapped user
Reexamination Certificate
2001-10-12
2004-07-13
Chan, Wing (Department: 2643)
Telephonic communications
Including aid for handicapped user
C379S088040, C704S271000
Reexamination Certificate
active
06763089
ABSTRACT:
BACKGROUND OF THE INVENTION
TECHNICAL FIELD OF THE INVENTION
This invention relates to telecommunications systems for the hearing impaired, and more specifically to a system and method for enabling communications through a public telecommunications network between a party using a TDD device and a party not so equipped.
There are various networks, public and private, that may be used for telephone communication. The public system we are all familiar with is often referred to as the public switched telephone network (PSTN).
FIG. 1
(prior art) is a simplified block diagram illustrating the basic configuration of an exemplary PSTN
100
. In general terms, PSTN
100
typically comprises numerous local exchanges, which may also be referred to as central offices (COs). Each CO is connected to dozens or even hundreds of telephone service subscribers, although for simplicity only two are shown in
FIG. 1
, designated as party
1
and party
2
. (The terms “user” and “subscriber” will be used interchangeably herein.) COs may be connected to each other either directly or though other telephone offices in order to properly route telephone calls. Two or more COs may be connected by a tandem office (TO), which may be viewed as the next higher level in a hierarchical network structure. A primary toll center may connect the various COs and tandems of a particular telephone company and themselves be connected to primary toll centers operated by others (not shown). The primary toll centers (PTC) of a given region may be connected to a sectional toll center (STC), a number of which may be connected with a regional toll center (not shown). Note that the illustrated PSTN
100
hierarchy is exemplary and is not employed in all systems. Where it exists, however, calls are usually routed through the lowest common switching level, with higher level offices used only for calls that are to terminate outside of the network below them. Party
1
and party
2
are typically but not necessarily located at a home or business site. In this illustration, party
1
may be the calling party and party
2
the called party. The call between them may be connected from their respective COs through a tandem office. Note the majority of telephone calls are two-party calls. The calling party initiates the process by opening up a dedicated circuit that will be used until the call is completed. This is true even where one or both of the parties are not human, such as when one fax machine ‘calls’ another. In some cases, more than two parties may be present on a call, and such a call may be in that event initiated by a phone-company operator. Note that the system and method of the present invention is equally applicable to these multiple-party telephone calls as well, but such applications will not be discussed separately herein.
Party
1
initiates the call by ‘going off hook’, which in many cases is accomplished simply by raising the handset from it's hook, but may also be accomplished in other way such as depressing a calling button on the telephone, annunciating a voice command, or similar steps. Going off hook completes a circuit between party
1
's telephone set and the CO, which is then ready to receive instructions on how to set up the remainder of the call circuit.
These instructions are given by the caller ‘dialing’ the telephone number of the called party. On a rotary telephone, this is actually accomplished by turning a spring-loaded dial and letting it return to its original position. Other phones are capable of instead producing a distinctive tone, or more specifically a pair of tones corresponding to each of its numbered keys. The pair of tones is sometimes referred to as a dual tone multi-frequency (DTMF) signal, and is recognizable by the PSTN. A caller using one of these touch-tone phones simply depresses the keys corresponding to a telephone number in order to place a call.
When the CO receives dialing instructions, it proceeds to set up the call. It determines the location of the called party in terms of the path that a connection to them must take. If party
2
is connected to the same local office as party
1
, the connection may simply be established through the local office and goes no higher in the network hierarchy. If not, the next highest level of the network is used, and then the next highest, and so on, on until the call can be placed. The connection is maintained until the parties go on hook when the call is completed. The various network lines used for the call are then freed for other uses.
Very useful for voice communication, as it is used by most of the population, PSTN
100
is obviously of little use for those who are without the ability to hear or speak or, as is sometimes the case, without either ability. For them the wonders of instant conversation go unrealized without some additional facility. Although modern telephone networks are now capable of transmitting data as well as voice, practical limitations often still prevent conversation-like communications. For example, telephones are ubiquitous while fax machines and computers are not as readily available. To send a fax message, the intended recipient must also have a fax machine, and of course one that is turned on and already connected to a phone line. While it is not uncommon for businesses to have such situation, the fax machine frequently remains unattended, with fax messages picked up only on an occasional basis. Even where an attendant continually monitors the machine, the intended recipient is likely someone else and must await delivery. And a fax message cannot be returned until it is received by the intended recipient. Fax machines in residences are often even less helpfully situated, many of them remaining unconnected until a through a voice conversation the sender and the recipient coordinate having it hooked up to a free line so that the fax message can be sent at an agreed upon time. For these reasons, fax machines are usually not a suitable substitute for a voice conversation.
Personal computers, while increasingly common in both home and office, have similar limitations in providing conversation-quality communications. Sending electronic mail (email) messages is a form of communicating with many advantages, but actual conversation is only achieved under certain circumstances. Note that as used herein, the terms ‘conversation’ and ‘conversation quality’ connote the ability for two (or more) parties to engage in a series of communications in a single communication session in which all parties participate substantially simultaneously. In the context of voice communication this is naturally possible, though it can also be achieved (albeit with some awkwardness) by repeated faxes or emails sent back and forth between parties in attendance at the proper devices at the same time. Computers connected to a communication network also offer the ability to ‘chat’, where two or more parties type in text messages that are with no significant delay displayed on the monitors of intended recipients. Again, however, absent a coincidence of users availing themselves of the same facility at the same time, chat sessions must be by advance arrangement.
Fortunately, however, a device has been developed to permit conversation between persons who are hearing (or speech) impaired. Often referred to as a telephone device for the deaf (TDD), it may be connected to a standard phone line. A TDD is a basically a telephone instrument that sends and receives text instead of voice communications. (TDDs are sometimes referred to as TTYs after the ‘teletypewriters’ on which they were originally modeled.) An exemplary TDD is illustrated in
FIG. 2
(prior art). There, TDD
200
features a keyboard
210
used by callers to enter text for transmission. A visual display
220
may be used to read the text that is being entered and, of course to read responsive text messages as they are received. The display—may be larger than that illustrated in
FIG. 2
, but its size is limited by the desired level of portability for the instrument. Acoustic
Chan Wing
Nortel Networks Limited
Smith Kevin L.
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