Patents by Inventor Siegfried G. Hitzler

Siegfried G. Hitzler has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 4791664
    Abstract: A system for selectively receiving incoming telephone calls to a phoneset includes an automatic answering device which answers all incoming calls by placing a simulated phone load across the phone lines. The answering device also enables a dual tone multifrequency (DTMF) receiver to receive tone frequencies input by a caller. The DTMF receiver decodes the tone pulses into binary coded decimal values which are stored in successive storage registers. A comparator compares the values stored in the registers with a respective code input by the subscriber and outputs a signal when the code dialed in by the caller matches the code input by the subscriber. The signal activates an electronic ringer circuit which serves to alert the subscriber of the presence of an authorized call. An off-hook detector detects the pick-up of a phoneset by the subscriber and acts to disable the electronic ringer circuit.
    Type: Grant
    Filed: September 12, 1986
    Date of Patent: December 13, 1988
    Inventors: Joseph M. Lutz, Siegfried G. Hitzler