Loading patent…
AssigneeInternational Business Machines Corporation
InventorsAugust P. Arneth, Curtis L. Foshee
Estimating the term…
Disclosed are a method and apparatus for exchanging information between a data terminal equipment (DTE) and data circuit terminating equipment (DCE) or controller connected to the data terminal equipment over a communications line. The specific information to be exchanged is the information indicating the delay period between a request to send received at the DCE and a clear to send condition occurring sometime later in response to the request to send. This function is normally handled by separate signalling lines, but for the so-called mini interface, no clear to send communication line exists. A method and apparatus employed in the present invention utilizes the transmitter signal element timing or clock line to convey the information from the DCE to the DTE. In response to receipt at the DCE of a request to send signal from the DTE, the DCE temporarily stops the transmitter signal timing clock, thus preventing the DTE from transmitting data. When the DCE modem has established carrier frequency and has completed its synchronization routine, a clear to send condition exists and the delay inherent between a request to send and clear to send signal is over. To signal this condition without the use of a clear to send signalling line, the DCE re-enables the transmitter signal element timing clock. The clock remains enabled at all times except during the request to send/clear to send delay period.
In a data communications system interface defining the connection between two communicating terminals or systems comprising a local unit and a remote unit, and in which the communications interface includes a time clock signal output line and a request to send line but does not include a separate external control line for granting to a remote requesting station a clear to send authorization control signal, but does include a fixed delay period timing element for generating an internal clear to send authorization control signal responsive to the elapse of a fixed delay period the improvement comprising:
In a data communications system interface defining the connection between two communications terminals or systems comprising a local unit and a remote unit, and in which the communications interface includes a timing clock signal output line and a request to send line but does not include a separate control line for granting to a remote requesting station a clear to send authorization control signal, an improved method of indicating the delay period between a request to send signal receipt and an establishment of carrier synchronization and frequency so that transmission may begin, comprising steps at said local unit of:
Dependencies are inferred from the claim text.