Data communication system
First Claim
1. A system for communicating over a telephone line between a host station and one of a plurality of remote stations, said system comprising:
- a remote terminal connected to said telephone line at said remote station, said remote terminal including frequency-shift-keyed decoder means connected to said telephone line for generating a data signal corresponding to a frequency-shift-keyed signal received from said telephone line, a visual display generator producing a visual signal corresponding to a visual representation that displays information received in the form of said frequency-shift-keyed signal and visual display means for receiving said visual signal and displaying said visual representation, said remote terminal further including a keypad having a plurality of keys and a two-tone signal generator connected to said telephone line for applying to said telephone line pairs of tones, each uniquely corresponding to one of said keys, card reader means for generating a digital signal indicative of information recorded on a card adapted for insertion in said card reader means, and a frequency-shift-keyed modulator connected to said card reader means and said telephone line applying a frequency-shift-keyed signal to said telephone line corresponding to the digital signal received from said card reader means; and
a host terminal connected to said telephone line at said host station, said host terminal including a frequency-shift-keyed modulator connected to said telephone line applying a frequency-shift-keyed signal to said telephone line corresponding to a data signal received from an external source and a two-tone decoder connected to said telephone line, said decoder generator a data byte identifying the tone pair being received, said host terminal further including a frequency-shift-keyed decoder connected to said telephone line generating a digital signal corresponding to the frequency-shift-keyed signal received from said remote terminal, thereby identifying the information recorded on said card.
3 Assignments
0 Petitions
Accused Products
Abstract
A data communication system including a central host terminal and a large number of remote terminals communicating with the host terminal through telephone lines. The remote terminal decodes frequency-shift-keyed signals and modulates an RF generator to display the data represented by the FSK signals on a conventional television screen. The remote terminal also includes a keypad and conventional two-tone signal generator for transmitting data to the host terminal. The remote terminal may also include a card reader and a frequency-shift-keyed modulator for generating FSK signals corresponding to information magnetically recorded on a card. The host terminal includes a TOUCH-TONE decoder for providing data signals indicative of the information from the remote terminals, an FSK decoder for generating data signals indicative of the information contained on cards read by the remote terminals, and an FSK modulator for transmitting FSK signals to the remote terminals. The FSK modulator in the host terminal switches from one frequency to another only at the zero crossings of the signal in order to prevent unwanted harmonics from being generated on the telephone lines. In order to allow the remote terminals to transmit alphanumeric data, a number of twelve-key keypads may be combined using circuitry which generates a keypad-identifying signal each time a key is pressed to uniquely identify the depressed key.
-
Citations
18 Claims
-
1. A system for communicating over a telephone line between a host station and one of a plurality of remote stations, said system comprising:
-
a remote terminal connected to said telephone line at said remote station, said remote terminal including frequency-shift-keyed decoder means connected to said telephone line for generating a data signal corresponding to a frequency-shift-keyed signal received from said telephone line, a visual display generator producing a visual signal corresponding to a visual representation that displays information received in the form of said frequency-shift-keyed signal and visual display means for receiving said visual signal and displaying said visual representation, said remote terminal further including a keypad having a plurality of keys and a two-tone signal generator connected to said telephone line for applying to said telephone line pairs of tones, each uniquely corresponding to one of said keys, card reader means for generating a digital signal indicative of information recorded on a card adapted for insertion in said card reader means, and a frequency-shift-keyed modulator connected to said card reader means and said telephone line applying a frequency-shift-keyed signal to said telephone line corresponding to the digital signal received from said card reader means; and a host terminal connected to said telephone line at said host station, said host terminal including a frequency-shift-keyed modulator connected to said telephone line applying a frequency-shift-keyed signal to said telephone line corresponding to a data signal received from an external source and a two-tone decoder connected to said telephone line, said decoder generator a data byte identifying the tone pair being received, said host terminal further including a frequency-shift-keyed decoder connected to said telephone line generating a digital signal corresponding to the frequency-shift-keyed signal received from said remote terminal, thereby identifying the information recorded on said card. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. A system for communicating over a telephone line between a host station and one of a plurality of remote stations, said system comprising:
-
a remote terminal connected to said telephone line at said remote station, said remote terminal including frequency-shift-keyed decoder means connected to said telephone line for generating a data signal corresponding to a frequency-shift-keyed signal received from said telephone line, a visual display generator producing a visual signal corresponding to a visual representation that displays information received in the form of said frequency-shift-keyed signal and visual display means for receiving said visual signal and displaying said visual representation, said remote terminal further including a keypad having a plurality of keys and a two-tone signal generator connected to said telephone line for applying to said telephone line pairs of tones, each uniquely corresponding to one of said keys, said frequency-shift-keyed signal received by said remote terminal from said telephone lines has a high-frequency signal corresponding to a bit at one logic state of said data signal received by said host terminal and a low-frequency signal corresponding to a bit at another logic state of said data signal received by said host terminal, and said frequency-shift decoder means in said remote terminal includes squaring means for producing a substantially square wave in received frequency-shift-keyed signal, said square wave having transitions substantially corresponding to the zero-crossing of said received frequency-shift-keyed signal, a first differentiator for differentiating high-to-low transitions of said square wave and generating a first transition indicator signal, a second differentiator for differentiating low-to-high transitions of said square wave and generating a second transition indicator signal, a frequency detector for measuring the time interval between successive signals of said first and second transition indicator signals, and comparing said measured interval to a predetermined time constant to determine if said measured interval corresponds to said high-frequency or low-frequency signal, said frequency detector generating a frequency indicator signal, and a flip-flop having a data input receiving said frequency indicator signal and a clock input receiving said first and second transition signals for generating an output data signal corresponding to said data signal received by said host terminal from an external source; and a host terminal connected to said telephone line at said host station, said host terminal including a frequency-shift-keyed modulator connector to said telephone line applying a frequency-shift-keyed signal to said line corresponding to a data signal received from an external source and a two-tone decoder connected to said telephone line, said decoder generating a data byte identifying the tone pair being received.
-
-
14. A system for communicating over a telephone line between a host station and one of a plurality of remote stations, said system comprising:
-
a remote terminal connected to said telephone line at said remote station, said remote terminal including frequency-shift-keyed decoder means connected to said telephone line for generating a data signal corresponding to a frequency-shift-keyed signal received from said telephone line, a visual display generator producing a visual signal corresponding to a visual representation that displays information received in the form of said frequency-shift-keyed signal and visual display means for receiving said visual signal and displaying said visual representation, said remote terminal further including a keypad having a plurality of keys and a two-tone signal generator connected to said telephone line for applying to said telephone line pairs of tones, each uniquely corresponding to one of said keys, said frequency-shift-keyed signal received by said remote terminal from said telephone line has a high-frequency signal corresponding to a bit at one logic state of said data signal received by said host terminal and a low-frequency signal corresponding to a bit at another logic state of said data signal received by said host terminal, and said frequency-shift decoder means in said remote terminal includes zero-crossing detector means for detecting zero-crossings of said received frequency-shift-keyed signal and generating a zero-crossing indicator signal, frequency detector means responsible to said zero-crossing indicator signal for detecting said high-frequency and low-frequency signals of said frequency-shift-keyed signal, and generating a frequency indicator signal, and pulse generator means responsible to said zero-crossing indicator signal and said frequency indicator signal for generating an output data signal corresponding to said data signal received by said host terminal from an external source; and a host terminal connected to said telephone line at said host station, said host terminal including a frequency-shift-keyed modulator connected to said telephone line applying a frequency-shift-keyed signal to said line corresponding to a data signal received from an external source and a two-tone decoder connected to said telephone line, said decoder generating a data byte identifying the tone pair being received. - View Dependent Claims (15, 16, 17, 18)
-
Specification