Method and system for selectively accessing multiplexed data transmission network for monitoring and testing of the network

A method for accessing data of a desired data channel in a multiplexed data stream transmitted over a predetermined transmission path and containing a predetermined pattern of framing signals and data from a plurality of data channels at predetermined data channel locations relative to the pattern of framing signals in the multiplexed data stream, the method comprising the steps of:

• providing a line access module in series with the transmission path for the multiplexed data stream;
• developing in the line access module, a data signal identical in data content to the data content of the multiplexed data stream without disturbing the transmission of the multiplexed data stream through the line access module;
• detecting the framing signals in the developed data signal;
• generating a control signal designating one of the plurality of data channels as the desired data channel;
• receiving the developed data signal and locating the designated one of the plurality of data channels in the developed data signal in response to the control signal and to the detected framing signals without disturbing the transmissionof the multiplexed data stream through the line access module;
• selectively opening the transmission path through the line access module and rerouting the multiplexed data stream around the line access module from a receiving side to a transmitting side thereof and through a gating cirucit connected in parallel with the line access module;
• and,
• selectively controlling the gating means to remove the data in the desired, located data channel without disturbing transmission of the remaining data channels in the multiplexed data stream.

Apparatus for testing a desired channel of a plural channel time division multiplexed data transmission system in which a plurality of channels containing data are multiplexed to form a multiplexed data stream which is transmitted over a multiplexed data transmission path, the apparatus comprising:

• gating circuit means having a multiplexed data input terminal, a multiplexed data output terminal and a control terminal, the gating means being responsive to a gating signal applied to the control terminal to selectively block passage to the multiplexed data output terminal of a signal applied to the multiplexed data input terminal;
• line access means having receiving and transmitting terminals connected in series with the multiplexed data transmission path to open the transmission path between the receiving and transmitting terminals and route the data stream from the receiving terminals to the input terminal of said gating circuit means, the multiplexed data output terminal of the gating circuit means being connected to the transmitting terminals of the line access means;
• means for generating a control signal designating one of the plurality of channels as the desired channel;
• means for detecting the framing signals in the multiplexed data stream;
• means responsive to the control signal and the detected framing signals for generating a gating signal specifying the location of the desired channel in the multiplexed data stream;
• means for applying said gating signal to the control terminal of said gating circuit means to block passage of the data in the desired channel from the multiplexed data input terminal to the multiplexed data output terminal of the gating circuit mean, whereby transmission of the desired channel can be selectively blocked without disturbing transmission of the remainder of the data stream.

In a time division multiplex signal transmission system for transmitting, over a signal transmission path, a multiplexed signal stream containing a predetermined pattern of framing signals interleaved with information bearing signals from a plurality of sources to thereby form a plurality of time multiplexed signal channels, a system for selectively blocking transmission of the signals in a desired one of the plurality of signal channels comprising:

• means for generating a control signal designating one of the plurality of signal channels as the desired one of the channels;
• means connected to the signal transmission path for detecting the framing signals in the multiplexed data stream;
• control circuit means responsive to the control signal and the detected framing signals for generating a gating signal specifying the location of the desired one of the plurality of signal channels in the multiplexed signal stream;
• gating circuit means connected in the signal transmission path and having a multiplexed data input terminal connected to receive the multiplexed signal stream from the signal transmission path, a multiplexed data output terminal connected to transmit signals passed by the gating circuit means onto the signal transmission path, and a control input terminal connected to receive the gating signal from the control circuit means, the gating circuit means selectively passing and blocking the passage of the multiplexed signal stream from the multiplexed signal input terminal to the multiplexed signal output terminal in response to the gating signal from the control circuit means, whereby passage of the signal in the desired one of the plurality of signalchannels is selectively blocked.