Modem with improved handshaking capability

Claim 2

In a method of operating a first data communications device to establish communication between said first data communications device and a second data communications device, which includes the step of said first and second data communications devices establishing data communications in a first predetermined communications mode, a method of testing said second data communications device for an ability to communicate in a second predetermined data communications mode, comprising the steps of: (a) causing said first data communications device to transmit a first predetermined set of one or more data words in said first predetermined data communications mode, said data words in said first predetermined set each corresponding to nonprinting characters; (b) causing said first data communications device to respond to subsequent receipt of a second predetermined set of data words by switching to operation in said second predetermined data communications mode; and (c) alternatively causing said first data communications device to remain in said first predetermined data communications mode in response to subsequent receipt of one or more data words which are not part of said second predetermined set of data words.

Claim 3

The method of claim 1 wherein: said first predetermined data communications mode is an asynchronous communications mode and said second predetermined data communications mode is a synchronous communications mode.

Claim 4

The method of claim 2 wherein: each of said data words in said first predetermined set of data words is selected from the group consisting of ASCII characters space, backspace, and null.

Claim 5

In a modem of the type including apparatus for handshaking according to a predetermined protocol to establish data communications with a remote data communications device in a first predetermined data communications mode of operation, and apparatus for selectively causing said modem to communicate in a second predetermined data communications mode of operation, the improvement comprising in combination: means operable when said modem is in an answer mode in said first predetermined data communications mode of operation to transmit a first predetermined set of data words corresponding to nonprinting characters in response to initial establishment of said first predetermined data communications mode of operation with said remote data communications device; receiving means for detecting received data words from said remote data communications device; and control means responsive to a predetermined number of the first ones of said received data words to be detected subsequent to transmission of said first predetermined set of data words for causing said modem to switch to said second predetermined data communications mode of operation in response to said first ones of said received data words matching a second predetermined set of data words and, alternatively, for causing said modem to remain in said first predetermined data communications mode of operation in response to said first ones of said received data words failing to match said second predetermined set of data words.

Claim 6

In a modem of the type including apparatus for handshaking according to a predetermined protocol to establish data communications with a remote data communications device in a first predetermined data communications mode of operation, and apparatus for selectively causing said modem to communicate in a second predetermined data communications mode of operation, the improvement comprising in combination: means operable when said modem is in an answer mode in said first predetermined data communications mode of operation to transmit a first predetermined set of data words corresponding to nonprinting characters in response to initial establishment of said first predetermined data communications mode of operation with said remote data communications device; receiving means for detecting received data words from said remote data communications device; and control means responsive to a predetermined number of the first ones of said received data words to be detected subsequent to transmission of said first predetermined set of data words for causing said modem to switch to said second predetermined data communications mode of operation in response to said first ones of said received data words matching a second predetermined set of data words and, alternatively, for causing said modem to remain in said first predetermined data communications mode of operation in response to said first ones of said received data words failing to match said second predetermined set of data words.

Claim 7

A modem as recited in claim 4 wherein: said control means is further responsive to said first ones of said received data words failing to match said second predetermined set of data words to transmit said first ones of said received data words to a data utilization device connected to said modem.

Claim 10

The method of claim 6 wherein said forst predetermined sequence comprising a space character and a backspace character.

Claim 11

The method of claim 7 wherein said first predetermined sequence further comprises a null character.

Claim 12

The method of claim 7 wherein said second predetermined sequence comprises said character and said backspace character.

Claim 13

The method of claim 9 wherein said second predetermined sequence further comprises a null character.

Claim 14

The method claim 10 wherein said first predetermined sequence further comprises said null character.

Claim 15

The method of claim 6 wherein said first operating mode comprises sending control information.

Claim 16

The method of claim 12 wherein said control information comprises data compression schemes available.

Claim 17

The method of claim 12 wherein said control information comprises designation of a data compression scheme to be used.

Claim 18

The method of claim 12 wherein said control information comprises designation of asynchronous communications or synchronous communications.

Claim 19

In am odem of the type including apparatus for handshaking according to a predetermined protocol to establish communications in a first operating mode with a remote modem, the improvement comprising: means operable when said modem is in first operating mode to transmit a first predetermined sequence of nonprinting characters to said remote modem; receiving means for detecting a second predetermined sequence of nonprinting characters from said remote modem; and control means responsive to detection of said second predetermined sequence for causing said modem to switch to a second operating mode wherein said modem and said remote modem may exchange control information and, alternatively, responsive to a lack of detection of said second predetermined sequence for causing said modem to remain in said first operating mode.

Claim 20

In am odem of the type including apparatus for handshaking according to a predetermined protocol to establish communications in a first operating mode with a remote modem, the improvement comprising: means operable when said modem is in first operating mode to transmit a first predetermined sequence of nonprinting characters to said remote modem; receiving means for detecting a second predetermined sequence of nonprinting characters from said remote modem; and control means responsive to detection of said second predetermined sequence for causing said modem to switch to a second operating mode wherein said modem and said remote modem may exchange control information and, alternatively, responsive to a lack of detection of said second predetermined sequence for causing said modem to remain in said first operating mode.

Claim 21

The improvement of claim 16 wherein said first predetermined sequence comprises a space character and a backspace character.

Claim 22

The improvement of claim 17 wherein said first predetermined sequence further comprises a null character.

Claim 23

The improvement of claim 17 wherein said second predetermined sequence comprises said space character and said backspace character.

Claim 24

The improvement of claim 19 wherein said second predetermined sequence further comprises a null character.

Claim 25

The improvement of claim 20 wherein said first predetermined sequence further comprises sain null character.

Claim 26

The improvement of claim 16 wherein said control information comprises the data compression schemes available.

Claim 27

The improvement of claim 16 wherein said control information comprises a data compression scheme to be used.

Claim 28

The improvement of claim 16 wherein said control information comprises selection of asynchronous communications and synchronous communications.

Claim 29

In a modem of the type including apparatus for handshaking according to a predetermined protocol to establish communications in a first operating mode with a remote modem, the improvement comprising: receiving means for detecting a first predetermined sequence of nonprinting characters; transmitting means tranmitting a second predetermined sequence of nonprinting charactes; and control means responsive to detection of said first predetermined sequence for causing said transmitting means to send said second predetermined sequence and for causing said modem to switch to a second operating mode wherein said modem and said remote modem may exchange control information and, alternalively, responsive to a lack of detection of said first predetermined sequence for causing said modem to remain in said first operating mode.

Claim 30

In a modem of the type including apparatus for handshaking according to a predetermined protocol to establish communications in a first operating mode with a remote modem, the improvement comprising: receiving means for detecting a first predetermined sequence of nonprinting characters; transmitting means tranmitting a second predetermined sequence of nonprinting charactes; and control means responsive to detection of said first predetermined sequence for causing said transmitting means to send said second predetermined sequence and for causing said modem to switch to a second operating mode wherein said modem and said remote modem may exchange control information and, alternalively, responsive to a lack of detection of said first predetermined sequence for causing said modem to remain in said first operating mode.

Claim 31

The improvement of claim 25 wherein said first predetermined sequence comprises a space character and a backspace character.

Claim 32

The improvement of claim 26 wherein said first predetermined sequence further comprises a null character.

Claim 33

The improvement of claim 26 wherein said second predetermined sequence comprises said space character and backspace character.

Claim 34

The improvement of claim 28 wherein said second predetermined sequence further comprises a null character.

Claim 35

The improvement of claim 29 wherein said first predetermined sequence further comprises said null character.

Claim 36

The improvement of claim 25 wherein said control information comprises the data compression schemes available.

Claim 37

The improvement of claim 25 wherein said control information comprises a data compression scheme to be used.

Claim 38

The improvement of claim 25 wherein said control information comprises selection of asynchronous communications and synchronous communications.