Networking computers via shared use of voice telephone lines

Details Networking computers via shared use of voice telephone lines Networking computers via shared use of voice telephone lines

1997-11-17

1998-11-24

Chan, Wing F.

Telephonic communications

Telephone line or system combined with diverse electrical...

Having transmission of a digital message signal over a...

379 9001, 370488, H04M 1100

Patent

active

058418415

DESCRIPTION:

BRIEF SUMMARY
This invention relates to a method for transmitting data from a computer on a telephone line simultaneously with the transmission of voice communications on the same telephone line and to a coupling apparatus for connecting the computer and the voice communication set to the telephone line.
The invention relates to interconnection and networking of remote personal computers for the purpose of gaining access to a central computer file server and for access to the computer data internet. The term personal computer will be used to include a work station or other data terminal equipment with an interface for connection to a local area network (LAN). The disclosed interconnection method permits a single computer or a plurality of computers at a remote location to be connected to a central computer network using existing telephone wires which continue to provide the normal voice access to the public switched telephone network (PSTN). In contrast to voice band data modems and fax machines, the disclosed connection method permits simultaneous use of the data network and the voice network. Use of the telephone wires for data network access does not at any time preclude origination or reception of a voice call on the PSTN and, similarly, use of voice access to the PSTN does not preclude access to the data network. The functions of ringing, talking and dial pulse or tone signaling operate normally and simultaneously with data transmission. The disclosed data connection method allows the personal computer to be continuously connected to a data network rather than periodically connected on a "dial up" basis.


BACKGROUND OF THE INVENTION

Computer data networks which provide data paths among personal computers that are localized to a single building or a small group of physically close buildings are referred to as a local area network or LAN. Computer networks that are composed of an interconnected set of LANs within a somewhat larger area such as an industrial park, a university campus or a small community are typically referred to in the art as a metropolitan area networks or MAN. A computer network covering an interurban or regional area is referred to as a wide area network WAN while the interconnection of WANs at the global level is referred to as the Internet.
The prior art includes several examples of remote access to computer networks. The use of voice band modems for remote connection to a computer network has been commonplace for many years. Most common is dial up access which is temporary and prevents simultaneous use of the telephone line for voice service. The prior art also includes leased line service which necessitates a separate telephone line for data service in addition to the normal telephone line used for voice service. Both of the above mentioned access methods require a modem (modulator/demodulator), a relatively costly device which converts the data signal to a modulated voice frequency signal which is then suitable for transmission on the voice network. Voice frequency modems typically limit the data transmission speed to less than 30 kb/s and absolutely to less than 64 kb/s.
The prior art also includes short distance "data over voice" modems which modulate a sinusoidal carrier signal which has a frequency somewhat higher than the highest voice frequency signal. These systems provide continuous data access and permit simultaneous voice and data transmission on the telephone line between a voice station set and the voice switch. A frequency selective interface is used to prevent interference between the voice transmission and the data transmission. The transmission distance of these modems is typically less than 3.5 miles or 5.5 km. One example is the LDV-2 data over voice multiplexor manufactured by RAD Data Communications which has a range of 9 km at 9600 b/s. A second example is described in U.S. Pat. No. 4,670,874 (Sato) which discloses the use of a modem to generate modulated data signals on a sine wave carrier together with a filter system which acts to separate the data transmission from

REFERENCES:
patent: 4534039 (1985-08-01), Dodds et al.
patent: 4670874 (1987-06-01), Sato et al.
patent: 4757495 (1988-07-01), Decker et al.
patent: 4785448 (1988-11-01), Reichert et al.
patent: 4799213 (1989-01-01), Fitzgerald
patent: 4901342 (1990-02-01), Jones

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