Data communications network testing system

A testing unit for connection in a data communications network at a location intermediate a central location and a remote location, a control unit at the central location including means for transmitting test control word signals and for responding to test response signals and the network including means for conveying signals between the central and intermediate locations and between the intermediate and remote locations, said testing unit comprising:

• A. first connection means for connection to the conveying means from the central location, the signals at said first connection means being one of either analog or digital signals,
• B. second connection means for connection to the conveying means from the remote location the signals at said second connection means being the other of the analog or digital signals,
• (A)C. first conversion means for converting analog signals to digital signals,
• (B)D. second conversion means for converting digital signals to analog signals,
• (C)E. configuration control means for generating one of a plurality of configuration signals thereby to designate which of the analog and digital signals are at said first and second connection means,
• (D)F. testing means responsive to test control word signals in digital form for generating test response signals in digital form, and
• (E)G. gating means responsive to the configuration signals for interconnecting said first and second connection means, said first and second conversion means and said testing means,
• i. said gating means connecting said first connection means to said testing means through said first and second conversion means when said testing unit is connected with analog signals at said first connection means, and
• ii. said gating means connecting said second connection means to said testing unit through said first and second conversion means when said testing unit is connected with digital signals at said first connection means.

Apparatus for testing the level of a signal on a data transmission means at a remote location in response to a test control signal from a central location in a data communications network, said apparatus being located at the remote location and comprising:

• A. first means for establishing an acceptable range of signal levels,
• B. second means connected to the data transmission means for generating continously a line level signal in response to the signals on the data transmission means,
• C. means connected to said first means for generating a status signal that indicates when the line level signal is within the predetermined range, and
• D. means responsive to the receipt of the test control signal for transmitting a message back to the central location that indicates the status of the line level signal and thereby the level of the signals on the data transmission means.

A method for testing the level of a signal on a data transmission means at a remote location in response to a test control signal from a central location in a data communications network, said method comprising the steps of:

• A. establishing at the remote location an acceptable range of signal levels,
• B. generating continuously at the remote location a line level signal in response to the signals on the data transmission means,
• C. generating at the remote location a status signal that indicates when the line level signal is within the predetermined range, and
• D. responding at the remote location to the receipt of the test control signal by transmitting from the remote location a message to the central location that indicates the status of the line level signal and thereby the level of the signals on the data transmission means.

In a data communications network for interconnecting a central location and at least one remote location through an intermediate location wherein the central location includes test means for modulating a test carrier signal with a test control word, wherein each remote site includes a modem including testing circuits and a remote testing unit for controlling the remote modem testing circuits and wherein the intermediate location includes an upstream modem, a downstream modem and circuit means responsive to binary signals for interconnecting the upstream and downstream modems, each upstream and downstream modem having testing circuits, the improvement of an intermediate testing unit for connection to each modem at the intermediate location, each said testing unit including:

• A. configuration control means for generating a first configuration signal when the corresponding modem is an upstream modem and a second configuration signal when the corresponding modem is a downstream modem,
• B. testing means for generating a test response signal in response to a test performed on the corresponding modem, said testing means including:
• i. means responsive to the test control word for generating a selection signal when the test control word identifies the testing unit,
• ii. means responsive to the selection signal and first and second groups of the commands for generating the test response signal in response to signals from the modem testing circuits,
• iii. means responsive to the selection signal and the second configuration signal for generating a special command signal,
• iv. means responsive to the special command signal and the second group of commands for altering the response of the testing circuits in the modem to these commands, and
• v. means responsive to the special command signal and predetermined ones of the second group of commands for substituting a command thereby to alter the test control signals that are transmitted to a remote testing unit.