Pulse or digital communications – Transceivers – Modems
Reexamination Certificate
1997-10-24
2001-10-23
Lather, William (Department: 2664)
Pulse or digital communications
Transceivers
Modems
C375S257000, C379S093060, C379S093090
Reexamination Certificate
active
06307880
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
This invention relates generally to telecommunication equipment for exchanging voice and data information. More particularly, the invention relates to the hardware equipment requirements for facilitating the switching between voice and data modes during a communication session.
2. Present State of the Art
Telephone communications systems traditionally facilitate the exchange of voice information between telephone users. As the telephone network or infrastructure expanded to provide a well developed and wired network for telephonic communicators, other technologies were also emerging. For example, digital devices such as computers, and more particularly personal computers, proliferated in their own digital domain. Furthermore, collocated computers, or computers located physically nearby other computers, were interconnected using traditional networking techniques such as local area networks. Physically interconnecting remote computers by employing dedicated interconnections often proved impractical or infeasible as interconnection alternatives.
Traditional telephonic networks employed switching mechanisms conducive for transmission of analog signals such as voice. Direct transmission of digital signals having fast rise and fall times were not conducive to the analog propagation characteristics of telephonic networks. To overcome such limitations, devices were developed to transform digital data, characteristic of computer data, into analog formats capable of propagation across traditional telephonic networks. Such transformation equipment became known as modems (modulator/demodulator) which generated analog signals compatible with the telephonic network. As the telephonic network was well developed as a product of the flourishing interconnection of telephone devices, the telephonic network became a compatible interconnection mechanism for interconnecting remote digital data equipment such as personal computers.
In a typical telephonic infrastructure, a specific user location, such as a telephonic location, is interconnected with other members of the telephonic network via a single interconnection path. While additional interconnection paths may be brought to a specific user location, additional communication interconnections result in additional and generally unnecessary expenses to a user. Interconnection sharing techniques emerged in order to accommodate a shared use of a single network interconnection by an analog device, such as a telephone, and a data device, such as a personal computer.
FIG. 1
illustrates a typical shared interconnection topology for accommodating both telephonic interconnections and data interconnections via a single interconnected network path. In
FIG. 1
, a telephone network
14
, illustrated as the public switched telephone network (PSTN), provides the interconnection matrix for routing between local and remote users. Telephone network
14
provides interconnection paths, such as telephone lines
28
and
30
, through which local and remote parties are interfaced or interconnected. Since telephone lines
28
and
30
provide only a single interconnection path, a local host
10
, such as a personal computer, and a telephone
20
may be alternatively switched and thereby interconnected with telephone line
28
. A remote host
18
, such as a personal computer, and telephone
24
must also be multiplexed or alternatively switched to utilize the unitary telephone line
30
. To facilitate mixed communication of both voice and data information, switches or multiplexing devices have been employed. However, facilitating both voice and data communication during a single communication session requires additional complexity and functionality.
One such implementation for accommodating both voice and data transmissions during a single communication session is the Voiceview industry standard. The Voiceview protocol was developed and published by the Radish Company, and is the most widely used protocol for switching between voice and data modes during a single communications session. The Voiceview mode provides for voice and data communications over a conventional telephone line and facilitates dynamic switching between voice and data modes during a single conversation session. Commercially available modems have incorporated the Voiceview technology and are readily available.
FIG. 1
illustrates a Voiceview modem
12
having a voice connection for voice line
22
and a date line connected to the local host
10
. Traditional Voiceview modems provide for a single interface to the telephone network such as that illustrated by telephone
28
.
In
FIG. 1
, a local user initiates a communication session by dialing a remote user using telephone
20
. Voiceview modem
12
and Voiceview modem
16
default to a voice communication session interconnection for routing voice communication between telephone
20
and telephone
24
. When a local user resolves to transmit data to the remote user, the local user prompts local host
10
to inform Voiceview modem
12
to initiate Voiceview commands to Voiceview modem
16
which designates a request to switch the communication path from a voice communication path to a data communication path. A sampling of Voiceview commands includes initialization of Voiceview parameters, a designation of facsimile or Voiceview data protocols to be employed during data transition, acknowledgements such as error status, flow control selections, and reset capabilities. A full listing of Voiceview commands and Voiceview operational specifics are available from modem chip set manufacturers that have incorporated the Voiceview technology into their commercially available chip sets. Such chip set vendors include, among others, Rockwell Semiconductor System. Additional Voiceview information is also available from Radish Communication Systems, Inc. and yet other modem and chip set manufacturers easily ascertainable by those of skill in the art.
In addition to the software functionality incorporated into the Voiceview-capable modems and modem chip sets, hardware capable of physically switching and thereby routing the communications from telephone line
28
to the appropriate voice or data terminal has also been required by Voiceview modems.
FIG. 2
represents a prior art configuration of traditional Voiceview modems. A host
40
such as a personal computer, provides a data and control environment for interfacing with a Voiceview modem
42
. Voiceview modem
42
incorporates traditional modem hardware
44
such as a bus interface device (generally implemented as an application specific integrated circuit (ASIC)). Traditional Voiceview modem
42
has been further comprised of a telephone line modem jack
56
for interfacing directly with telephone line
46
of telephone network
14
. Voiceview hardware
48
, responsive to the Voiceview functionality incorporated within the software of traditional modem hardware
44
such as a modem chip set, facilitates the switching between voice and data communications during a single communications session. A telephone connector
54
facilitates the routing of voice communication via a voice line
50
to telephone
52
.
While external or larger dimensioned modems have more easily accommodated the inclusion of Voiceview hardware
48
, the inclusion of such additional hardware on a smaller integrated form factor modem, such as a PCMCIA modem, becomes intolerable and excessively expensive for purchasers of Voiceview capable modems. While inclusion of Voiceview functionality into a modem chip set requires that additional memory resources be allocated to such functionality, the major deterring factor for incorporation of Voiceview functionality remains the inclusion of additional hardware switching elements into the physically constrained form factor of modern miniaturized modems.
Thus, what is needed is a method and system for providing switching between voice and data communications as directed by modem hardware without incurring the additional burdens associated with
Evans John P.
Messerly Shayne
3Com Corporation
Lather William
Workman & Nydegger & Seeley
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