Theft alarm for vehicle carried radio equipment

• US 4,035,765 A
• Filed: 06/14/1976
• Issued: 07/12/1977
• Est. Priority Date: 06/14/1976
• Status: Expired due to Term

• Current Assignee: Able Manufacturing Company Incorporated
• Original Assignee: Able Manufacturing Company Incorporated
• Inventors: Brassfield, John R., Wenner, Lance E.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Groody, James J.
• Application Number:
  US05/695,647
• Time in Patent Office: 393 Days
• Field of Search: 340/63, 340/276, 340/253 B, 340/280, 340/64, 340/65, 180/114, 307/10 AT, 325/117, 325/312
• US Class Current: 340/428
• CPC Class Codes: B60R 2025/1016 Remote signals alerting owner or authorities, e.g. radio signals
• CPC Class Codes: B60R 25/00 Fittings or systems for preventing or indicating unauthorised use or theft of vehicles locks for vehicles E05B77/00-E05B85/00
• CPC Class Codes: B60R 25/04 operating on the propulsion system, e.g. engine or drive motor
• CPC Class Codes: B60R 25/10 actuating a signalling device
• CPC Class Codes: B60R 25/1004 Alarm systems characterised by the type of sensor, e.g. current sensing means using door lock sensors B60R25/1001
• CPC Class Codes: B60R 25/102 a signal being sent to a remote location, e.g. a radio signal being transmitted to a police station, a security company or the owner
• CPC Class Codes: G08B 13/1445 with detection of interference with a cable tethering an article, e.g. alarm activated by detecting detachment of article, breaking or stretching of cable furniture, e.g. shelves for displaying merchandise, incorporating tethers to prevent theft A47F7/024, A47F5/0861
• CPC Class Codes: G08B 13/22 Electrical actuation

Abstract

A theft alarm is provided for use in conjunction with vehicular mounted radio equipment, such as the popular but too frequently stolen citizens'"'"' band transceivers, which is responsive to either physical separation of the equipment being protected from the common electrical ground provided by the chassis of the vehicle or disconnection from such equipment of the cable by which it is normally coupled with an antenna mounted on the same vehicle. In order to permit locating and/or coupling the alarm circuit components with the equipment at points remote from the latter, so that the alarm portion of the system may be in a protected location or its presence not revealed by "extra" wires leading directly to the equipment or both, and in order that the alarm may function reliably and immediately in response to an attempted theft without adversely affecting the transmission of radio frequency signals between the equipment and the antenna and without possible impairment of the functioning of the alarm due to spurious electrical paths, the cable for connecting the equipment to the antenna is electrically separated into two sections at a zone intermediate its length, at which zone each conductor of one section is capacitatively coupled with the corresponding conductor of the other section, and the alarm controlling circuit is then coupled between the common ground and one of the conductors of the section of the antenna cable electrically adjacent to the equipment to be protected.

Claims

1. For use in combination with:

a vehicle having an electrically conductive chassis providing a local, electrical, ground reference;

an electrical direct current power source carried by said vehicle and having a pair of power terminals of which one is electrically connected with said ground reference;

electrically actuatable horn means carried by said vehicle and having a pair of energizing terminals of which one is electrically connected with said ground reference;

radio equipment means normally carried by said vehicle and having a ground terminal normally electrically connected with said ground reference when said equipment means is being carried by said vehicle, and a pair of antenna terminals of which one is electrically connected with said ground terminal of said equipment means; and

antenna means carried by said vehicle and having a pair of connection terminals of which one is electrically connected with said ground reference;

apparatus for operatively coupling said antenna terminals of said equipment with said connection terminals of said antenna means and for providing a theft alarm to protect said equipment means against unauthorized removal from said vehicle by providing an alram indication whenever said ground terminal of said equipment means is electrically disconnected from said ground reference, said apparatus including;

first cable means having a pair of electrical conductors respectively releasably electrically connected adjacent one end of said first cable means with said antenna terminals of said equipment means;

second cable means having a pair of electrical conductors respectively electrically connected adjacent one end of said second cable means with said connection terminals of said antenna means;

a relay having a coil provided with a pair of operating terminals of which one is electrically connected with the other of said power terminals and the other of which is electrically coupled with one of said conductors of said first cable means,

said relay including a switch which is open when said coil is energized and closed when said coil is deenergized and having a pair of switch terminals of which one is electrically connected with said other power terminal and the other of which is electrically connected with the other of said energizing terminals of said horn means;

first electrical coupling means adjacent the other ends of said first and second cable means for electrically coupling the other conductor of said first cable means with one conductor of said second cable means; and

second electrical coupling means adjacent the other ends of said first and second cable means comprising a capacitor interconnected between said one conductor of said first cable means and the other conductor of said second cable means for electrically intercoupling said cables for radio frequency signals while maintaining direct current isolation between said other operating terminal of said coil and said other conductor of said second cable means,

whereby said one conductor of said first cable means is employed both as a part of the radio frequency signal transmission line between said equipment means and said antenna means and as a part of the alarm controlling circuit without impairment of either function thereof by the other.

2. The invention of claim 1, wherein said first electrical coupling means comprises another capacitor interconnected between said other conductor of said first cable means and said one conductor of said second cable means.

3. The invention of claim 2, wherein said capacitors are of substantially equal capacitance to maintain the transmission line balance between the conductors of said first and second cable means for radio frequency signals.