Real-time digital signal processing relative to multiple digital communication channels

A system for providing information telecommunication services between an information handling center and multiple diversely equipped user terminals remotely linked to said center through the public switched telephone network comprising:

• at least one time division multiplexed digital carrier trunk having a plurality of time channels and providing access via said time channels for transferring digitized log PCM signals between said system and said remote user terminals via said public telephone network in diverse digital forms compatible with corresponding diverse signalling requirements and characteristics of equipment at said remote user terminals;
• said log PCM signals being incompatible in form with information signal processing requirements of said center;
• and
• all-digital signal processing means coupling said center with said trunk, and operating in response to programmable instructions for exchanging signals with said center in forms directly compatible with information signal processing requirements of said center, for exchanging signals with said trunk time channels in forms directly compatible with signal requirements and characteristics of said remote user terminals, and for converting said signals in transit between said center and said trunk time channels into forms respectively compatible with requirements of said center and said remote user terminals;
• said signal processing means comprising:
• first digital signal processing means interfacing with said center, and second digital signal processing means interfacing with said trunk time channels;
• first and second random access memory arrays, one memory array allocated for storing data and the other memory array reserved for holding the instructions executable by signal processing means;
• means cyclically coupling said first and second signal processing means with said memory arrays in time-staggered fashion whereby said first and second processing means alternate in performing operations relative to said data as directed by said instructions;
• interruption control means coupling said first and second processing means for enabling said first and second processing means to exchange interrupt requests, and for enabling said first processing means and center to exchange interrupt requests;
• and
• means responsive to interruption requests presented by said interruption control means for enabling said first and second processing means to exchange data through said data storing memory array, whereby said first processing means may be operated to process data prepared by said center for one of said user terminals and said second processing means may be operated to further process said data so that each said processing means may operate thereby to partially convert the signal form of said data to to prepare the data for transmission to the user terminal via a time channel on said digital trunk.

A system for providing information telecommunication services between an information handling center and multiple diversely equipped user terminals remotely linked to said center through the public switched telephone network comprising:

• at least one time division multiplexed digital carrier trunk having a plurality of time channels and providing access via said time channels for transferring digitized log PCM signals between said system and said remote user terminals via said public telephone network in diverse digital forms compatible with corresponding diverse signalling requirements and characteristics of equipment at said remote user terminals;
• said log PCM signals being incompatible in form with information signal processing requirements of said center;
• and
• all-digital signal processing means coupling said center with said trunk, and operating in response to programmable instructions for exchanging signals with said center in forms directly compatible with information signal processing requirements of said center, for exchanging signals with said trunk time channels in forms directly compatible with signal requirements and characteristics of said remote user terminals, and for converting said signals in transit between said center and said trunk time channels into forms respectively compatible with requirements of said center and said remote user terminals;
• said signal processing means comprising:
• means for selectively handling signals representing digitized speech or sound data;
• said means including means for performing compression and decompression conversions on said signals whereby said signals can be stored in a compressed form at said center, in order to conserve usage of storage facilities at said center, and transmitted over said trunk in decompressed form.

A communication system for transmitting data between an information handling center and multiple diversely equipped user terminals remotely linked to said center through parts of the public switched telephone network comprising;

• a host data processing system at said center;
• at least on time division multiplexed digital carrier trunk having a plurality of channels and providing access for said center with said public telephone network;
• said trunk carrying digitized signals in Log PCM form representing quantized samples of analog signals with diverse characteristics relating to the characteristics of equipment at said user terminals;
• and
• all-digital signal processing means at said center for transferring data and control signal between said host system and time channels on said trunk, and for performing modem conversions on said data signals in transit between said host system and trunk time channels;
• said conversions serving to adapt said center to diversity of equipment at remote user terminals by presenting data signals for transmittal over said trunk in forms directly receivable at said user terminals and by presenting data signals to be processed by said host data processing system in a form directly suited to processing applications at said system;
• said signal processing means comprising first and second digital signal processors, random access instruction storing memory coupled to both said digital signal processors for holding instructions to be used by both and coupled to said host system for receiving instruction program loads for said digital signal processors from said host system, a random access data storing memory coupled to both digital signal processors for holding data to be accessed by either or both digital signal processors and coupled to both said host system and said trunk for exchanging data with said host system and said trunk;
• said instruction and data memories having recurrent cycles of accessibility in which alternate cycles are normally allocated to said first and second digital signal processors in an interleaved manner;
• so that each digital signal processor can retrieve instructions from instruction memory without interrupting or slowing operations in the other digital signal processor and so that each digital signal processor can fetch data for data memory and write date to data memory without interrupting or slowing operations in the other digital signal processor;
• and
• cycle steal control means coupled to said digital signal processors, data memory, said host system and said trunk for determining when a cycle of access to said data memory is not required by either digital signal processor, and for selectively allocating said cycle to either said host system or the trunk, whereby data can be exchanged between said host system and data memory between data memory and trunk in a cycle steal mode having the effect of not interrupting or slowing operations in either digital signal processor.