Automatic switching unit for data communications network

An automatic switching unit for connecting an interfacing unit to a data communications network including a primary transmission path, a secondary transmission path and data coupling means connected to the secondary transmission path, the data coupling means transmitting a first status signal when data coupling means are active and the interfacing unit transmitting a condition signal when it is active, said automatic switching unit comprising:

• A. switching means having stable and astable states and including:
• i. a primary switching means for connecting, in its stable state, the interfacing unit to the primary data transmission path, and
• ii. secondary switching means for connecting, in its astable state, the interfacing unit through the data coupling means to the secondary data transmission path, and
• B. switch control means including:
• i. means for generating a control signal that shifts said primary and secondary switching means to their astable states in response to the status signal from the data coupling means, and
• ii. resetting means connected to said switch control means for terminating the control signal in response to the condition signal thereby to enable said switching means to return to their stable states and re-establish the connection with the primary transmission path.

An automatic switching unit for connecting an interfacing unit to communications network including a primary transmission path and a secondary transmission path, the interfacing unit transmitting a condition signal when it is active, said automatic switching unit comprising:

• A. switching means having stable and astable states and including:
• i. a primary switching means for connecting, in its stable state, the interfacing unit to the primary transmission path, and
• ii. a secondary switching means for connecting, in its astable state, the interfacing unit to the secondary data transmission path,
• B. coupling means for connecting said secondary switching means to the secondary transmission path, including means for transmitting a first status signal in response to a first condition on the secondary data transmission path, and
• C. switch control means including:
• i. means connected to said coupling means for generating a control signal that shifts said switching means to their astable states in response to the first status signal from said coupling means, and
• ii. resetting means connected to said switch control means for terminating the control signal in response to the condition signal thereby to enable said switching means to return to their stable states and re-establish the connection with the primary transmission path.

An automatic switching unit for connection in a data communications network including a central site, at least one remote site, a primary data transmission path between the central site and each remote site, a secondary data transmission path between the central site and a remote site, a remote site including a modem with modulation and demodulation means and a testing means with means for detecting the receipt of a modulated carrier test signal in the testing unit, said automatic switching unit including

• A. primary switching means for connection in circuit between the modulation and demodulation means in the modem and the primary data transmission path,
• B. secondary switching means for connection in circuit between the modulation and demodulation means in the modem and the secondary transmission path, and
• C. switch control means that connect to the secondary transmission path for controlling said primary and secondary switching means, said switch control means including
• i. means responsive to a first condition on the secondary transmission path for transmitting an on-hook signal,
• ii. means responsive to the on-hook signal and second conditions on the secondary data transmission path for transmitting a data mode signal,
• iii. means responsive to the on-hook signal for opening said primary switching means to thereby disconnect said modem and the primary data transmission path,
• iv. means responsive to the on-hook signal and the data mode signal for transmitting an answer back tone over the secondary transmission path,
• v. means responsive to the receipt of the on-hook signal and data mode signal for closing said secondary switching means to establish communications over the secondary data transmission path, and
• vi. resetting means for terminating the on-hook signal to re-establish transmission over the primary data transmission path, said resetting means including
• a. an interval timer to disable said on-hook signal transmitting means at the end of a predetermined interval, and
• b. means responsive to the absence of the first condition on the secondary transmission path, the absence of an answer back signal, and the absence of either of the on-hook signal or carrier detection signal for enabling said timer to complete the interval and disable the on-hook signal transmitting means.

A method for controlling communications in a data communications network that includes a central site with a data unit for transmitting and receiving the communications and a switching unit, a remote site, and a primary communications path that normally is used during communications between the central and remote sites, said method comprising the steps, in order, of:

• A. establishing, at the central site, communications between the switching unit at the central site and an alternate communications path from the remote site that is in parallel with the primary communications path,
• B. establishing, at the remote site, communications between the remote site and the alternate communications path in response to said establishment of communications between the switching unit and the alternate communications path,
• C. isolating the remote site from the primary communications path after communications are established between the switching unit at the central site and the remote site over the alternate communications path, and
• D. activating the switch unit to establish communications between the data unit and the remote site over the alternate communications path.

Apparatus for controlling communications in a data communications network that includes a central site, a remote site, and a primary communications path that normally is used during communications between the central and remote sites, said apparatus comprising:

• A. switching means at the central site,
• B. means at the central site for establishing communications between said switching means and an alternate communications path from the remote site that is in parallel with the primary communications path,
• C. means at the remote site for establishing communications between the remote site and the alternate communications path in response to the establishment of communications between said switching means and the alternate communications path, and
• D. means for isolating the remote site from the primary communications path after communications are established over the alternate communications path, said switching means establishing communications between the central site and the alternate communications path after said isolating means are activated.

A method for controlling communications in a data communications network that includes a central site, a remote site, a primary communications path that normally is used during communications between the central and remote sites, and means at the central site for transmitting and receiving data signals and test signals, the test signals defining test commands and test data, said method comprising the steps of:

• A. establishing communications for the test and data signals between an alternate communications path between the remote site and the central site, the alternate communications path being in parallel with the primary communications path,
• B. establishing, at the remote site, communications between the remote site and the alternate communications path in response to said establishment of communications between the central site and the alternate communications path,
• C. isolating the remote site from the primary communication path after communications are established over the alternate communications path, both the data signals and test signals thereafter being communicated between the central and remote sites over the alternate communications path, and
• D. thereafter switching the communications of the data signals between the primary communications path and the alternate communications path in response to first and second of the test commands that are conveyed to the remote site over the alternate communications path.

Apparatus for controlling communications in a data communications network that includes a central site, a remote site, a primary communications path that normally is used during communications between the central and remote sites and means at the central site for transmitting and receiving data signals and test signals, the test signals defining test commands and test data, said apparatus comprising:

• A. means for establishing communications for the test signals and the data signals between an alternate communications path from the remote site and the central site, the alternate communications path being in parallel with the primary communications path,
• B. means for establishing, at the remote site, communications between the remote site and the alternate communications path in response to said establishment of communications between the central site and the alternate communications path,
• C. means for isolating the remote site from the primary communications path after communications are established over the alternate communications path, and
• D. means for controlling the transfer of data signals between the remote site and the primary communications path in response to first and second of the path commands.