Abstract: A communication system embodying the invention has a communication channel with at least two ends, one end of the channel being connected to a transmission device with relatively limited computational capacity and an other end of the channel being connected to a computer having relatively large computational capacity. The transmission device includes a signal source node; a set of M−1 delay buffers connected in series and defining a set of M progressively delayed signal nodes, M being a positive integer, one end of the series of M delay buffers being connected to the signal source node; a set of M parallel downsampling operators connected to the M progressively delayed signal nodes; and, a parallel-to-serial converter having M parallel inputs and a single serial output, the M parallel inputs being connected to the outputs of the M parallel downsampling operators and the single serial output being coupled to the one end of the communication channel.

Abstract: Continuously variable slope delta modulation coding uses a thresholder having an analog input and a digital output representing the relationship between a signal amplitude at the analog input and a predetermined threshold. An integrator has an output and one input connected to the output of the thresholder and a second input that receives a step size value, the output of the integrator corresponding to a product of the thresholder output and the step size value. An adder has one input that receives an analog input signal that is to be encoded and a second input connected to the output of the integrator. The output of the adder is coupled to the analog input of the thresholder. A step size controller is responsive to an analog signal level related to the analog input signal for varying the step size value in response to variations in the analog signal level.