Digital pushbutton signalling receiver

Details Digital pushbutton signalling receiver Digital pushbutton signalling receiver

H - Electricity

04

M

379/20

H04M 1/26 (2006.01) H04Q 1/457 (2006.01)

Patent

CA 1155985

ABSTRACT Disclosed is a digital signalling receiver responsive to an input in-band audio frequency signal digitized at a first sampling frequency and containing pushbutton telephone (PB) signals, each of which consist of one select- ed out of a predetermined plurality of lower group of frequencies and the other one out of a predetermined plurality of higher group of frequencies The whole frequency range of the audio frequency signal is split into two frequency bands in response to the digitized signal, one band is eliminated, and a consequent signal is produced lying within the other band and containing both or either of the lower and higher groups of frequencies of the PB signals. The consequent signal is resampled a predetermined number of times at a second sampling frequency obtained by reducing by 1/2 each time the first sampling frequency and the frequency band signal not containing the lower and higher groups of frequencies of the PB signals are eliminated, thereby generating two sets of signals, one containing frequencies lowered corresponding to the lower group of frequencies and the other one, containing frequencies lowered corresponding to the higher group of frequencies. The two sets of split signals are fed to two sets of band-pass filter groups for detecting predetermined PB signals which in turn feed energy extracting circuits. The PB signals ale deter- mined from the outputs of the energy extracting circuits.

375974

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