Abstract: A data communications method and system is provided to facilitate the communication between a plurality of units of data terminal equipment (DTE) connected over communication lines. A first DTE unit is located in a digital network and a second DTE unit is located in either a digital network or in an analog network. When attempting to place a call from the first DTE unit in the digital network to the second DTE unit in either a digital network or an analog network, a first call is made to determine the characteristics of the second DTE unit called. If the second DTE unit called returns an indication that it also possesses digital capability, then the call is established. If, however, the indication from the second DTE unit called is that it does not have digital capability, then the first DTE unit places a second call through a modem within a terminal adapter within the system to the second DTE unit. The system is also capable of receiving a call made to the first DTE from outside the digital network.

Abstract: Disclosed is a data compressing modem for connection to a decompressing modem over communication lines. The compressing modem receives an input data stream, and each character in the data stream is recodified with a compressed character code, the length of which is dependent on the frequency of the character in the data stream. A frequency table is maintained so that changes in the relative frequency of characters in the data stream will be recognized by the compressing modem and the compressed character codes representing such characters will be exchanged accordingly. A decompressing modem, which is connected over communication lines to the compressing modem, processes the compressed character code in a reverse order from the manner in which the compressing modem processing the codes. The decompressing modem also maintains a relative frequency table and as the relative frequencies of the various characters change, the actual characters represented by the compression codes must also change.

Abstract: A data telecommunications system and method is provided for sending a data stream of characters in distinct data packets between two units of data terminal equipment (which can be either terminals and/or computers) connected over communication lines. A modem is connected between each unit of data terminal equipment and the communication lines, and one initiating modem includes a means for changing the packet size of the data which is transmitted. The receiving modem checks the packets for errors, and if errors are found, the packet is retransmitted. The initiating modem counts the number of transmissions of data packets as well as the number of retransmissions of data packets. A ratio of retransmissions to transmissions is used to determine the optimum packet size. The packet size is continually subject to change as the ratio changes during transmission.

Abstract: Disclosed is a data telecommunications system and method in which at least one modem which, capable of operating at a variety of transmission speeds, selects the proper speed at which to operate. An initiating modem capable of operating at a plurality of operating speeds compares the maximum operating speed of a receiving modem, and if a match is found, operation begins at that operating speed. If no match is found, operation begins at a default transmission speed.

Abstract: A data telecommunications system and method is provided for sending a data stream of characters between two pieces of data terminal equipment (which can be either terminals and/or computers) connected over communication lines. A modem is connected between each piece of data terminal equipment and the communication lines, and at least one of the modems is capable of operating in both a special mode which provides optimized data transmission and a normal mode which provides direct non-optimized data transmission. Upon detection of a special mode indicating character, a modem of the data telecommunication system of the present invention will establish a link under the special mode protocol. In one embodiment, when a second special character is detected by the modem, the modem is caused to operate in a normal mode. In an alternate embodiment, the modem will store characters in a special buffer memory until either the special mode-indicating character is detected or until the buffer fills.