Visitor sensing device

• US 5,280,266 A
• Filed: 03/09/1992
• Issued: 01/18/1994
• Est. Priority Date: 03/09/1992
• Status: Expired due to Fees

• Current Assignee: Yao-Tzung Kao
• Original Assignee: Yao-Tzung Kao
• Inventors: Kao, Yao-Tzung
• Primary Examiner(s): Swarthout, Brent
• Application Number:
  US07/848,278
• Time in Patent Office: 680 Days
• Field of Search: 340/330, 340/326, 340/328, 340/331, 340/332, 340/286.11, 340/541, 340/565, 340/529, 358/108, 358/85, 379/171, 379/167, 379/53, 379/54
• US Class Current: 340/330
• CPC Class Codes: H04M 11/025 Door telephones adapted for television H04N7/186
• CPC Class Codes: H04N 7/186 Video door telephones

Abstract

A visitor sensing device capable of being combined with a conventional door intercom is provided. The device includes a detecting circuit to be installed adjacent a door of a house, for sensing the presence of a visitor standing in front of the door for a preset period of time. Responsive to detecting a visitor, the detecting circuit sends a signal to a converting circuit. The converting circuit converts the signal received from the detecting circuit into a monostable pulse to be fed to a vision circuit, which then displays an image of a visitor on its screen and also actuates an audio circuit. The audio circuit includes a buzzer to generate an audio signal.

Claims

1. A visitor sensing device disposed outside of a house adjacent a door thereof, comprising:

a detecting circuit for detecting the presence of a visitor in proximity to a door of a house, said detecting circuit having a output terminal for providing an output signal responsive to detection of said presence of a visitor for a time period greater than a predetermined time;

a converting circuit for converting said output signal from said detecting circuit to a monostable pulse signal, said converting circuit having an input terminal coupled to said output terminal of said detecting circuit, said converting circuit having an output terminal for providing said monostable pulse signal;

a vision circuit having an input coupled to said output terminal of said converting circuit for enabling a visual display monitor subsequent to a first predetermined delay time period responsive to receipt of said monostable pulse signal, said vision circuit including a first time delay circuit having an input terminal coupled to said output terminal of said converting circuit, said vision circuit further including a first switching circuit having an input coupled to an output terminal of said first time delay circuit and an output coupled to said visual display monitor for enabling visual display thereon responsive to an output signal from said first time delay circuit; and

,

an audio circuit having an input coupled to said output terminal of said first time delay circuit for energizing a buzzer subsequent to a second predetermined time delay period responsive to receipt of said output signal from said first time delay circuit, said audio circuit including a second time delay circuit having an input coupled to said output terminal of said first time delay circuit, said audio circuit further including a second switching circuit having an input coupled to an output terminal of said second time delay circuit and an output coupled to said buzzer for generating an audible signal subsequent to said second predetermined time delay.