Dial pulse restorer

A dial pulse restorer for controlling the functions of dictation apparatus operatively coupled to one end of a telephone line in response to telephone dial pulses which originate from a remote telephone that is connected to the other end of said telephone line and for disconnecting said dictation apparatus from said telephone line when said remote telephone hangs up, said dial pulse restorer comprising:

• means for generating transition pulses in response to telephone pulse transitions that are received over said telephone line, a pair of said telephone pulse transitions defining a telephone dial pulse and a single telephone pulse transition representing a hang-up pulse that is applied to said telephone line when said remote telephone hangs up;
• window generating means responsive to the first transition pulse of a pair of transition pulses to generate a window pulse of predetermined duration and substantially centered on the expected time of occurrence of the second transition pulse of said pair;
• control pulse generating means coupled to said window generating means and to said means for generating transition pulses, and responsive to a transition pulse that is generated during said window pulse duration to produce a control pulse for use in said dictation apparatus;
• and
• means for disconnecting said dictation apparatus from said telephone line in response to said window pulse if a transition pulse is not generated during said window pulse duration.

Apparatus for discriminating between telephone dial pulses and a telephone hang-up pulse applied to a telephone line, said telephone dial and hang-up pulses being susceptible to distortion such that at least the transitions that define said telephone dial pulse and the transition that defines said telephone hang-up pulse are received by said apparatus, comprising:

• shaping means for shaping the received transitions;
• window pulse generating means coupled to said shaping means and responsive to a transition for generating a window pulse at a predetermined time after said transition and of a duration encompassing the expected time of occurrence of the next following transition;
• means for generating a simulated telephone dial pulse if a transition occurs during said window pulse;
• and
• hang-up pulse detecting means responsive to a generated window pulse for indicating the receipt of a telephone hang-up pulse at a time delayed from said window pulse if a simulated telephone dial pulse is not generated during the time delay interval.