Telephonic communications – Telephone line or system combined with diverse electrical... – Having transmission of a digital message signal over a...
Reexamination Certificate
2002-06-28
2004-06-15
Chan, Wing Fu (Department: 2643)
Telephonic communications
Telephone line or system combined with diverse electrical...
Having transmission of a digital message signal over a...
C379S093260, C379S093080, C341S052000, C341S173000
Reexamination Certificate
active
06751303
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not applicable.
BACKGROUND OF THE INVENTION
The present invention relates in general to data communications over telephone voice channels, and, more specifically, to a method for signaling alphanumeric characters to an automated terminal using multiple frequency tones corresponding to standard DTMF tone frequencies.
Data communications over public switched telephone network connections typically depend upon modems at each end of the communication link. For authorizing credit card transactions, for example, a terminal at a vendor location dials a telephone number to contact a computer operated by a credit card company or bank. The vendor terminal transmits a credit card number and a charge amount. The bank terminal responds with either an authorization number or data indicating a refusal and the link is terminated. Thus, only a very small amount of data is typically exchanged (e.g., less than one hundred alphanumeric characters). Even at the slowest modem speeds, the data exchange occupies only a few seconds at most. A much greater length of time is taken up by modem initialization and synchronization (i.e., handshaking), which may take tens of seconds. Most such equipment operates at very slow modem speeds (e.g., 300 baud) because of the fact that modem synchronization occurs faster for slower modem speeds. Thus, it would be very beneficial to provide such point-to-point data communication in a way that avoids the delays of modem synchronization.
Telephone voice channels are also used by customers to order various goods or services to be delivered to the location from which they place the telephone call, such as pay-per-view cable television programs or groceries, for example. These types of orders are typically taken by a live person or utilize automated menu selections using touch-tone navigated menus, even though only a relatively small amount of data is being exchanged. Using a touch-tone system, it is very tedious to transmit data using a full character set because no more than 16 unique signals are available for transmission (i.e., the standard pairs of DTMF tones), and only 12 of these tones are available on most telephone devices. Consequently, the system expense, difficulty of use, and/or time span for placing an order may be too great to justify using such an ordering system.
SUMMARY OF THE INVENTION
The present invention has the advantages of enabling full alphanumeric communication with data processing equipment using only DTMF-capable devices and provides short transmission times without modem training, synchronization, or handshaking.
In one aspect of the invention, a multifrequency tone generator is provided for sending data over a telephone voice channel. An alphanumeric character generator sequentially generates alphanumeric characters. Preferably, the character generator may be a keypad or keyboard. A plurality of tone generators have a summed output for transmitting a tone signal selectably including a combination of standard DTMF frequency tones, but not restricted to always having both frequency tones usually paired together by standard DTMF tones. A translation circuit is responsive to an alphanumeric character from the character generator to activate the plurality of tone generators to produce a predetermined combination of the DTMF frequency tones corresponding to the alphanumeric character.
REFERENCES:
patent: 3936801 (1976-02-01), Shuman
patent: 4087638 (1978-05-01), Hayes et al.
patent: 5249220 (1993-09-01), Moskowitz et al.
patent: 5699417 (1997-12-01), Khojasteh
patent: 6115464 (2000-09-01), Lester et al.
patent: 6396921 (2002-05-01), Longster
patent: 1178657 (2002-02-01), None
patent: WO 200108397 (2001-02-01), None
Chan Wing Fu
Sprint Communications Company L.P.
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