Circuit for detecting dial pulses
AssigneeComex Systems, Inc.
InventorsGary N. Stapleford, Joel E. Sandahl
Life of this patent
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Abstract
A circuit for detecting dial pulses at a receiving telephone transmitted from a sending telephone after the telephones are interconnected. Detecting circuits, including bandpass filters and summing and threshold circuits transmit a probable pulse signal. A probable pulse signal indicates that the signals on the telephone line have the characteristics present whenever the dialing mechanism at the sending telephone is actuated. A digital correlation circuit receives all the probable pulse signals and advances a counter which stores the number representing the dialed digit if a correlation exists.
Claims25
A circuit for correlating an incoming sequence of pulses and a known pulse pattern, said correlation circuit comprising:
- receiving means for transmitting a sequence of probable pattern pulses in response to the incoming sequence of pulses, each probable pattern pulse corresponding to the incoming pulses,
- pattern means for providing, in a timed sequence, a plurality of control signals which correspond to the known pulse pattern, said receiving means enabling said pattern means to transmit the control signals in response to each probable pattern pulse,
- means responsive to a first probable pattern pulse in the sequence for synchronizing the operation of said pattern means and the probable pattern pulses, and
- correlation means responsive to said control signals transmitted by said pattern means upon receipt of successive probable pattern pulses from said receiving means for indicating whether the incoming pulse sequence correlates to the known pulse pattern.
A dial pulse detection circuit for detecting dial pulses transmitted over a telephone line by dialing a digit on a telephone dial actuator, said detection circuit comprising;
- input means connected to the telephone line for receiving signals including dial pulse signals therefrom,
- a plurality of detecting means connected to said input means, each said detecting means transmitting an output signal indicative of the amount of energy in a predetermined passband,
- probable pulse means for transmitting a probable dial pulse in response to the output signals from all of said detecting means,
- pattern means for providing, in a timed sequence, a plurality of control signals which correspond to a known dial pulse pattern, said pattern means being enabled to transmit the control signals in response to each probable dial pulse,
- correlation means responsive to the control signals transmitted by said control pattern means upon receipt of successive probable dial pulses for indicating whether the incoming dial pulse sequence correlates to the known dial pulse pattern, and
- digit storage means responsive to said correlation means for storing a number representing the digit dialed on the telephone dial actuator when a correlation exists.
A dial pulse detection circuit for detecting pulses with the characteristics of dial pulses transmitted over a telephone line by dialing a digit on a telephone dial actuator, said detection circuit comprising:
- input means connected to the telephone line to receive signals including dial pulses therefrom,
- a plurality of detecting means connected to said input means, each detecting means comprising a bandpass filter connected to receive signals from said input means and an absolute value conversion circuit in series with said bandpass filter, said bandpass filters having mid-frequencies at a reference frequency and the second and fourth harmonics thereof,
- summing means,
- a scaling means connecting the output of each of said absolute value conversion circuits to said summing means, and
- threshold means responsive to the output from said summing means for transmitting a probable pulse indicating that pulse with the characteristics of a dial pulse has been received.
Dependencies are inferred from the claim text.