Drop-and-insert multiplex digital communications system
AssigneeCoastcom
InventorsToney C. Warren, Michael E. Hance
Life of this patent
Estimating the term…
Abstract
Apparatus for dropping and inserting digital data in a time division multiplexed, serial data stream. A communications link is divided into two spans with an electrical switch connecting the two spans. Data is used to derive channel-timing information defining the time divisions or strobes of each of the multiplexed channels. The strobe pulses are used to toggle the switch so that local transmit-and-receive channels may be inserted and dropped in accord with the channel strobe pulses. The same channel strobe pulses used for transmitting local data are used for receiving data from the multiplexed bit stream. In the absence of channel strobe pulses, the switch connects the two links.
Claims10
A digital communications unit for use between spans in a serial data communications link comprising,
- data input and output means connected to spans in a communications link carrying a multiplex digital, multi-channel, serial, data stream, each channel having a fixed time duration in a data frame, each frame marked by framing bits, the data characterized by a data frequency, said input means extracting clock pulses from the data,
- a data switch connected between the data input and output means, said switch normally connecting the data input means to said output means, said switch having a selector for selecting data from the data input means or from a local transmit channel,
- circuit means connected to said data input means for generating channel strobe pulses by counting clock pulses, with reference to the framing bits, said channel strobe pulses having a pulse width corresponding to the duration of a channel, preselected strobe pulses being transmitted to the switch,
- a local transmit channel connected to the selector and to the timing circuit means, the channel being inserted in the data stream in response to a preselected strobe pulse through the data switch whereby said inserted local transmit channel replaces any data in said communications link during said preselected strobe pulse, and
- a delay means interposed between the data input means and the switch for synchronizing serial data of the data stream with the channel strobe pulses.
A digital communications unit for use between first and second spans in a serial data communications link comprising,
- data input means connected to a first span of a communications link for receiving a stream of multi-channel PCM data in data frames, each frame marked by framing bits and for deriving clock and data pulses from the PCM data,
- circuit means, connected to said data input means, for generating channel strobe pulses by counting clock pulses with reference to framing bits, said strobe pulses having a pulse width corresponding to each channel of said multi-channel PCM data,
- data output means connected to a second span of a communications link for transmitting the stream of PCM data to the second span,
- at least one numbered local transmit and receive channel, each connected to the timing circuit means for receiving said channel strobe pulses, each numbered receive channel connected to the data input means and operative upon receipt of a channel strobe pulse corresponding to the number of the numbered receive channel, thereby dropping a channel of receive data from the stream of PCM data,
- a data switch connecting said data input means to said data output means in a first position and connecting a numbered local transmit channel to said data output means in a second position, said data switch having a selector means for changing the switch from the first position to the second position upon receipt of a channel strobe pulse corresponding to the number of the numbered transmit channel, thereby inserting a channel of transmit data into the stream of PCM data, and
- a delay means interposed between the data input means and the data switch for synchronizing serial data of the data stream with the channel strobe pulses.
In a drop-and-insert digital communications unit for use in a time division multiplex span having multi-channel, serial data frames marked with framing bits, the span interrupted by a switch connecting an input means to a data output means, the improvement comprising,
- circuit means connected to the data input means, thereby receiving data frames, said data frames each marked by a framing bit, said circuit means for generating channel strobe pulses by counting clock pulses with reference to a framing bit, said channel strobe pulses having a pulse width corresponding to the duration of a channel, each channel in a frame represented by a channel strobe pulse,
- channel selection means connected to receive said channel strobe pulses for selecting one of the channels in data frames for drop and insert by applying a selected one of the strobe pulses to the switch connecting the data input means to the data output means in a communications span, and
- a delay equalization circuit means connected in the span for delaying data an amount equivalent to the circuit path delay for data travelling through the circuit means and the channel selection means.
Dependencies are inferred from the claim text.