US 4,071,708 A · Dial pulse detector

Abstract

A dial pulse detector apparatus accurately detects the occurrence of dial pulses in the presence of adverse line conditions resulting in severe signal distortions due to inductive effects, noise and loading by other pieces of equipment. Signals greater than two different selected threshold levels are examined for, and signals less than the lower threshold are also examined for. Signals greater than the threshold levels are counted up on a time duration basis and added in a weighting arrangement. Signals less than the lower threshold are counted on a time duration basis and are subtracted from the added signals. When the combined signal counts reach a first specified count a dial pulse break signal is recognized. Signal counting is continued and when the combined signal counts reach a second specified count a dial pulse make signal is recognized, thereby completing the detection of a dial pulse. Because of the weighting system it would be possible to erroneously record the occurrence of two dial pulses in a time interval when only one dial pulse could validly occur. This is prevented by the use of a real-time counter which forces a minimum recognition time for a dial pulse break signal.

Claims35

Dependent claims

Apparatus for detecting the occurrence of dial pulses on telephone lines in the presence of severe signal distortions due to line conditions, comprising in combination,

a. first means responsive to the occurrence of a first signal level greater than a first selected threshold level to generate first count signals at regularly occurring spaced time intervals during the continuance of said first signal level,
b. second means responsive to the occurrence of a second signal level less than said first selected threshold level to generate second count signals at regularly occurring spaced time intervals during the continuance of said second signal level,
c. up/down counting means having input and output means,
1. said first means being coupled to a part of said counting means input means and causing an up-count for each said first count signal,
2. said second means being coupled to a part of said counting means input means and causing a down-count for each said second count signal,
d. count signals interpreting means coupled to said counting means output means responsive to the detection of a selected up-count by said counting means followed by the detection of a selected down-count by said counting means to generate a dial pulse count signal designating that a valid dial pulse has been detected.

3 more elements

Apparatus for detecting the occurrence of dial pulses on telephone lines in the presence of severe signal distortions due to line conditions, comprising in combination,

a. up/down counting means having an up counting input, a down-counting input, a count clearing input, a low count output, an intermediate count output and a high count output,
b. up-count gate means having an input and an output, said output being operatively coupled to said counting means up-counting input, said up-count gate means being responsive to the occurrence at said gate means input of all signal levels greater than a first selected threshold level to generate up-count signals at regularly occurring spaced time intervals during the continuance of said signal level condition,
c. down-count gate means having an input and an output, said output being operatively coupled to said counting means down-counting input, and said down-count gate means being responsive to the occurrence at said gate means input of all signal levels less than said first selected threshold level to generate down-count signals at regularly occurring spaced time intervals during the continuance of said signal level condition,
d. up-count storage means having an input and an output, said input being operatively coupled to said counting means high count output, and being effective responsive to the registration in said counting means of said high count to store a high count indicator and generate a high count output signal at its output, said up-count gate means comprising at least first and second gate means, said first gate means being responsive as aforesaid to all signal levels greater than said first selected threshold level to generate up-counts, and said second gate means being responsive to the occurrence of all signals greater than a second selected threshold level greater than said first selected threshold level to generate up-count signals at regularly occurring spaced time intervals during the continuance of said second threshold level signals,
e. monitor means having inputs respectively operatively coupled to said counting means intermediate count output and to the output of said up-count storage means, and having an output operatively coupled to said counting means count clearing input, said monitor means being effective responsive to signals at its inputs indicating the occurrence of a stored high count followed by the occurrence of an intermediate count to clear said counting means to its said low count and generate a dial pulse signal.

2 more elements

Dependencies are inferred from the claim text.

Dial pulse detector

Life of this patent

Dial pulse detector

Life of this patent

Abstract

Claims35