Telecommunication device operating under an enhanced TDD protocol

• US 5,517,548 A
• Filed: 11/19/1993
• Issued: 05/14/1996
• Est. Priority Date: 05/20/1992
• Status: Expired due to Term

• Current Assignee: Ultratech Incorporated (Veeco Instruments Incorporated)
• Original Assignee: Ultratech Incorporated (Veeco Instruments Incorporated)
• Inventors: Engelke, Robert M., Schultz, Ronald W., Hilliard, Jeffrey, Vitek, Troy, Colwell, Kevin
• Primary Examiner(s): Chan, Wing F.
• Application Number:
  US08/155,061
• Time in Patent Office: 907 Days
• Field of Search: 379/52-54, 379/90, 379/93, 379/96-99, 379/110, 379/108, 340/825.19, 370/31, 370/24, 370/110.1, 375/8, 375/9, 375/91, 375/107, 375/114, 375/116, 375/121
• US Class Current: 379/52
• CPC Class Codes: H04M 1/2475 for a hearing impaired user
• CPC Class Codes: H04M 11/00 Telephonic communication systems specially adapted for combination with other electrical systems

Abstract

A telecommunication device for the deaf is designed to operate under an enhanced TDD communication protocol. The TDD is capable of communicating with conventional TDDs operating under normal Baudot/Weitbrecht communications, but is also capable of communicating with a similarly enhanced TDD utilizing an enhanced protocol with a faster data transfer rate. The enhanced TDD is capable of signaling to another remote TDD through the use of a synchronization character that it is capable of enhanced TDD communications. If a similar synchronization character is received from the remote station, both TDDs can then switch to enhanced TDD communication with its advantages of speed and enlarged character set. The synchronization character is especially designed so as not to interfere with the operation of a conventional TDD which might receive the character and also to be sufficiently distinctive so as to be capable of definite reception by enhanced TDD machines with minimum error.

Claims

1. An enhanced telecommunication device for the deaf (TDD) for communication over a telephone line, the device comprising

a source for input data characters to be transmitted;

a destination for received data characters;

a microprocessor operating in accordance with a stored program code and connected to accept input data from the input source and to deliver data characters to the destination;

an analog input line adapted to being connected to the telephone line so as to be responsive to the reception of Baudot tones over the telephone line and also connected to the microprocessor so as to provide a digital input to the microprocessor of the data received over the telephone line;

an analog output circuit adapted to being connected to the telephone line so as to be capable of presenting Baudot tones over the telephone line and also connected to receive data from the microprocessor and transmit Baudot tones encoding such data over the telephone line; and

a memory device connected to the microprocessor containing the program code for operation of the microprocessor to control operation of the telecommunications device to generally

(i) receive data entered from the input source,

(ii) present data entered from the input source on the analog output line,

(iii) receive data from the analog input line and

(iv) deliver data from the analog input line to the destination;

the program code further comprising code

(a) enabling communication under either a conventional Baudot protocol, which uses Baudot tones for sending data, which does not transmit a carrier on the telephone line when no data is being sent, and which transmits data at either 45.5 or 50 characters per second, or an enhanced TDD protocol which uses Baudot tones or sending data, which does not transmit a carrier on the telephone line when no data is being sent, and which operates at a data transmission rate in excess of 100 baud,

(b) causing a special synchronization sequence to be transmitted under the enhanced TDD protocol, the synchronization sequence being composed of one of the Baudot tones and an echo suppression tone, the synchronization sequence selected to not be recognized as a displayed character by a remote telecommunication device operating under conventional Baudot protocol, and

(c) causing the timing and format of communications to be in conventional Baudot protocol if no Baudot tone sequence is received in return from the remote telecommunication device indicating the capability to communicate in the enhanced TDD protocol and causing the timing and format of communication to be in the enhanced TDD protocol if a Baudot tone sequence is received in return from the remote telecommunication device indicating the capability to communicate in the enhanced TDD protocol.

2. A telecommunication device for the deaf as claimed in claim 1 wherein the enhanced TDD protocol includes mark bits and space bits of differing bit time intervals.

3. A telecommunication device for the deaf as claimed in claim 1 wherein the enhanced TDD protocol includes a seven-bit character and the character table from ASCII code.

4. A telecommunication device for the deaf as claimed in claim 1 wherein the enhanced TDD protocol synchronization sequence is a sequence of alternating mark tones which are 1400 Hertz and echo suppression tones which are neither 1800 nor 1400 Hertz.

5. A telecommunication device for the deaf as claimed in claim 4 wherein the enhanced TDD protocol synchronization sequence is a sequence of alternating mark tones which are 1400 Hertz and echo suppression tones which are neither 1800 nor 1400 Hertz, beginning with an echo suppression tone and alternating between echo suppression tones and mark tones until five mark tones have been transmitted.

6. A telecommunication device for the deaf as claimed in claim 1 wherein the program code further constrains the device to impose a pause after the synchronization sequence before the start of initial data transmissions to sense for receipt of a synchronization sequence from a remote device.

7. A telecommunication device for the deaf as claimed in claim 1 wherein the input source is a keyboard.

8. A telecommunication device for the deaf as claimed in claim 1 wherein the destination is a visually readable display.

9. An enhanced telecommunication device for the deaf (TDD) for communication over a telephone line, the device comprising

a source for input data characters to be transmitted;

a destination for received data characters;

a microprocessor operating in accordance with a stored program code and connected to accept input data from the input source and to deliver data characters to the destination;

an analog input line adapted to being connected to the telephone line so as to be responsive to the reception of Baudot tones over the telephone line and also connected to the microprocessor so as to provide a digital input to the microprocessor of the data received over the telephone line;

an analog output circuit adapted to being connected to the telephone line so as to be capable of presenting Baudot tones over the telephone line and also connected to receive data from the microprocessor and transmit Baudot tones encoding such data over the telephone line; and

a memory device connected to the microprocessor containing the program code for operation of the microprocessor to control operation of the telecommunications device to generally

(i) receive data entered from the input source,

(ii) present data entered from the input source on the analog output line,

(iii) receive data from the analog input line and

(iv) deliver data from the analog input line to the destination;

the program code further comprising code

(a) enabling communications under either a conventional Baudot protocol or an enhanced TDD protocol which transmits data using Baudot tones without transmitting a carrier when no data is being sent, the data being transmitted at a data transmission rate which exceeds an average rate of 100 baud and which includes mark bits and space bits of different bit time intervals,

(b) causing a special synchronization sequence to be transmitted under the enhanced TDD protocol, which sequence is made up of 1400 hertz tones and echo suppression tones, the sequence selected to be a sequence which is not recognized as a displayed character by a remote telecommunications device operating under conventional Baudot protocol, and

(c) causing the timing and format of communications to be in conventional Baudot protocol if no synchronization sequence is received in return from the remote telecommunications device and in enhanced TDD protocol if a synchronization sequence is received in return from the remote telecommunications device.

10. A telecommunication device for the deaf (TDD) comprising

a keyboard;

a visually readable display;

a microprocessor operating in accordance with a stored program code and connected to accept input data characters from the keyboard and to present data characters on the display;

an analog input circuit adapted to being connected to a telephone line so as to be responsive to the reception of Baudot tones over the telephone line and also connected to the microprocessor so as to provide a digital input to the microprocessor of the data received over the telephone line;

an analog output line adapted to being connected to the telephone line so as to be capable of presenting Baudot tones over the telephone line and also connected to receive data from the microprocessor and transmit Baudot tones encoding such data over the telephone line; and

a memory device connected to the microprocessor containing the program code for operation of the microprocessor to control operation of the telecommunications device to generally

(i) receive data entered from the keyboard,

(ii) present entered data from the keyboard on the analog output line,

(iii) receive input data from the input analog line and

(iv) display data from both the keyboard and the input analog line on the display;

the program code further comprising code enabling communication under either a conventional Baudot protocol or an enhanced TDD protocol, the enhanced TDD protocol using a seven-bit character set, using the Baudot tones of 1400 Hertz for a logical one and 1800 Hertz for a logical zero, and having a bit time for a space of 12 milliseconds and a bit time for a mark of 7 milliseconds.

11. A method of using a telecommunication device for sending characters received from a user over a telephone line to a recipient telecommunications device comprising the steps of

accepting a series of input characters from the user,

storing the series of characters in the form of digital data in memory in the telecommunications device,

transmitting the series of characters over a telephone line as a sequence of tones encoded in an enhanced TDD protocol in which (i) Baudot tones of 1400 and 1800 hertz are used to represent data bits when data is being sent with no tones being transmitted when no characters are being sent, (ii) the bit times for a logical space bit and for a logical mark bit are different in time so as to minimize the total time required for character transmission, (iii) each character is represented by seven bits, (iv) the characters are encoded using an ASCII character set, and (v) the average rate of character transmission is in excess of 100 baud, and

receiving sequence of tones at the recipient telecommunications device and decoding the series of characters therefrom.

12. A telecommunication device comprising

a keyboard for accepting a series of input characters from a user,

a display for displaying the characters which are input by the user,

a microprocessor connected to the keyboard and the display for receiving and displaying the series of characters,

a memory connected to the microprocessor for storing the series of characters and for storing program code for operation of microprocessor to control operation of the telecommunications device,

an analog output circuit connected to the microprocessor and adapted for linkage to a telephone line, the analog output circuit capable of generating Baudot tones of 1400 and 1800 hertz, and

the program code causing the microprocessor to direct the analog output circuit to transmit the series of characters onto the telephone line in an enhanced TDD protocol in which (i) Baudot tones of 1400 and 1800 hertz are used to represent data bits with no tones being transmitted when no characters are being sent, (ii) the bit times for a logical space bit and for a logical mark bit are different in time so as to minimize the total time required for character transmission, (iii) each character is represented by seven bits, (iv) the characters are encoded using an ASCII character set, and (v) the average rate of character transmission is in excess of 100 baud.