DTMF receiver

Details DTMF receiver DTMF receiver

1988-06-13

1989-05-23

Tokar, Michael J.

Electricity: measuring and testing

Measuring, testing, or sensing electricity, per se

Frequency of cyclic current or voltage

324 79R, 364200, G01R 2314

Patent

active

048333999

ABSTRACT:
A DTMF receiver (10) recognizes each of a plurality of multi-frequency tones, each tone centered on a predetermined standard frequency. Two digital bandpass filters (14, 16) each have four frequency bins, each frequency bin operating according to a recursive second-order transfer function for preferentially transmitting frequencies near the standard frequencies. Each frequency bin accumulates, for each of a plurality of sampling periods, respective spectral energy signals from the input signal. A temporal energy signal is derived from the spectral energy signals. For each bandpass filter (14, 16), a time-domain test template generator (30) and a frequency-domain test template generator (34) are provided to generate time-domain and frequency-domain test templates. These test templates are input to an analyzer (38) that compares the templates against data-adaptive frequency-domain and time-domain reference templates.

REFERENCES:
patent: 4445177 (1984-04-01), Bratt et al.
patent: 4455602 (1984-06-01), Baxter III
patent: 4493027 (1985-01-01), Katz et al.
patent: 4525780 (1985-06-01), Bratt
patent: 4570217 (1986-02-01), Allen et al.

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