Motorola Corporation

Itt Industries, Inc.

Robert Smith

Anthony D Newton

A subscriber line card arrangement, in which each of eight subscriber lines is interfaced by a respective high voltage analog circuit, followed by a low voltage circuit for producing essential analog functions including over-sampled analog-to-digital and digital-to-analog conversion. A single CMOS digital signal processor (DSP) is multiplexed between each of the eight channels to perform digitial signal processing of the telephone signals in each channel. Silicon usage for the high voltage functions is reduced as is the amount of bipolar analog circuitry. Digital hardware is saved by multiplexing the DSP. The invention is useful in central offices and PABX's.

Subscriber line card arrangement

Frequency controlled oscillator utilizing an U/D counter in the feedback

A digital FM demodulation circuit provides improved resolution by selecting from a group of at least four of the most recent samples, a subgroup of three samples. The first and last samples of the selected subgroup are summed and the sum is divided by the intermediate sample.

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Meyrin, Switzerland

Robert Smith