Master antenna line communication system

• US 3,932,858 A
• Filed: 07/25/1974
• Issued: 01/13/1976
• Est. Priority Date: 02/08/1973
• Status: Expired due to Term

• Current Assignee: Inn-Tronics
• Original Assignee: Inn-Tronics
• Inventors: Smith, James O., Gade, John J.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US05/491,656
• Time in Patent Office: 537 Days
• Field of Search: 340/280, 340/408, 340/413, 340/151, 340/152 T, 340/416, 340/167 A, 340/167 R, 340/216, 325/308, 179/15 BF, 179/15 AL, 179/175.3 F, 179/175.31 R
• US Class Current: 340/505
• CPC Class Codes: G08B 26/004 with common interrogation of substations

Abstract

A theft communication system is particularly useful for indicating the unauthorized disconnection of a television set or the like from any one of the rooms of a hotel or motel. The communication system includes a central transmitter connected with a master television antenna system for transmitting successive querying scan pulses to sensors located on the antenna line at the location of each television set. Each of the sensors is adapted to apply a reply signal to the antenna line if its sensing circuitry indicates that its associated television set has been disconnected therefrom. The time of reply of each of the sensors is different from that of any other, and the system further includes a receiver connected to the antenna line at a central location for receipt of such reply signals. Such receiver is synchronized with the transmitter so that it can distinguish between reply signals from different ones of the sensors, and is adapted to generate an alarm signal if and only if a sensor replies to two successive querying signals, thereby making the generation of a false alarm due to the appearance of noise on the antenna line as a reply signal exceedingly unlikely.

Claims

1. In combination with an antenna system having an antenna for receipt of a communication signal and a common antenna line connected between said antenna and a plurality of locations for common distribution of such communication signal to said plurality of locations;

transmitting means for generating a querying information signal different from said communication signal directly connected into said antenna like for distribution of such information signal over said line to said plurality of locations;

a plurality of sensors, each of which is connected to said antenna line at an associated one of said locations for receipt of said information signal and includes means responsive to receipt of said information signal by selectively generating and applying a reply information signal to said antenna line in response to a predetermined condition of the sensor circuitry;

receiving means connected to said antenna line for generating an alarm signal in response to receipt within a selected time interval of a predetermined number of reply information signals from any one of said sensors; and

means on said antenna line for preventing said information signal and any communication signal on said antenna line from interfering with one another;

said transmitting means continually generating successive querying signals and distributing the same over said antenna line to said plurality of sensors, and said receiving means generating said alarm signal in response to receipt of a pair of reply signals spaced in time from one another an interval indicative of one of said sensors generating said reply signals in response to succeeding ones of said querying signals;

each of said successive querying signals generated by said transmitting means being an electrical scan pulse having a predetermined time of initiation;

each of said sensors including timing means adapted to apply a reply signal to said antenna line if said predetermined condition of said sensor circuitry exists at a predetermined time after receipt thereby of said scan pulse, which predetermined time is different for each of said sensors;

said receiving means including means for distinguishing between reply pulses received from different ones of said sensors on the basis of the time at which said reply pulse is sent thereto after transmittal of an electrical scan pulse on said line;

power supply regulating means for receiving electrical power on said antenna line and regulating the same to provide an essentially constant power level for operation of said sensor; and

said timing means of each of said sensors including means providing a time constant for setting said time at which said sensor generates said reply signal after receiving said scan pulse signal, means for generating said reply signal after said predetermined time, and means responsive to the passage of said predetermined time as determined by said time constant means by causing said generating means to initiate said reply signal.

2. A communication system comprising transmitting means for generating a querying information signal, and a sensor responsive to receipt of said information signal by selectively generating a reply information signal, said sensor including timing means for sending said reply signal a predetermined time after said sensor receives said information signal;

and wherein said timing means includes means providing a time constant for setting said predetermined time a mono-stable multivibrator for generating said reply signal after said predetermined time, and a flip-flop drive responsive to the passage of said predetermined time as determined by said time constant means by driving said multivibrator to initiate said reply pulse, whereby minor changes in the threshold level of said multivibrator do not affect the timing of said reply pulse.

3. The communication system of claim 2 wherein said sensor further includes power supply regulating means for receiving variable power input and regulating the same to provide an essentially constant power level for operation of said sensor.

4. The communication system of claim 2 wherein said communication system includes a plurality of sensors, each one of which is located at a different location for receipt of an information signal from said transmitting means, said sensors including timing means adapted to send a reply signal at a predetermined time after receipt thereby of an information signal from said transmitting means, which predetermined time is different for each of said sensors;

and receiving means included as part of said communication system for receiving said reply signals, such receiving means including means for distinguishing between reply signals received from different ones of said sensors on the basis of the time at which said reply signal is sent thereto after transmission by said transmitting means of the information signal to which said reply signal is responsive; and

wherein said transmitting means continually generates said information signals and said receiving means generates an alarm signal after receipt thereby within a selected time interval of a predetermined number of reply signals from any one of said sensors.

5. The communication system of claim 4 wherein said receiving means is adapted to generate said alarm signal in response to receipt thereby of a pair of reply signals spaced in time from one another an interval indicative of one of said sensors generating said reply signals in response to succeeding ones of said information signals.