Antitheft system for a car stereo having a detachable grille

• US 5,323,139 A
• Filed: 04/01/1993
• Issued: 06/21/1994
• Est. Priority Date: 04/23/1992
• Status: Expired due to Term

• Current Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Original Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Inventors: Suenaga, Syoji, Isaki, Mikio
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): Oda, Christine K.
• Application Number:
  US08/040,442
• Time in Patent Office: 446 Days
• Field of Search: 340/426, 340/661, 340/568, 340/660, 340/686, 340/687
• US Class Current: 340/426.34
• CPC Class Codes: G11B 33/027 Covers G11B33/022 takes precedence; with means for guiding the record carrier G11B17/34
• CPC Class Codes: H04B 1/082 to be used in vehicles H04B1/086 takes precedence; holding or mounting accessories B60R11/02
• CPC Class Codes: H04B 2001/084 with removable front panel

Abstract

An antitheft system, for car stereo having a detachable grille, has an identification resistor provided in the body of the car stereo, and a resistor provided in the grille. A circuit including the identification resistor and the resistor in the grille is formed when the grille is attached to the body of the car stereo. A voltage across the identification resistor is compared with a reference voltage for producing a coincident signal when the voltage is equal to the reference. In response to the coincident signal, the car stereo becomes operative.

Claims

1. An antitheft system for a car stereo having a detachable grille attached to a body of the car stereo, the grille having operating switches for selecting operating modes of the car stereo, the antitheft system comprising:

a voltage supply circuit provided in the body of the car stereo;

an identification resistor provided in the body of the car stereo;

a resistor provided in the grille;

circuit means forming a circuit including the voltage supply circuit, the identification resistor and the resistor in the grille when the grille is attached to the body of the car stereo;

detector means for detecting a voltage across the identification resistor and for producing a coincident signal when the detected voltage is equal to a predetermined voltage;

actuating means responsive to the coincident signal for rendering the car stereo operative.

2. The system according to claim 1 wherein

said detector means comprises a comparator and a memory storing a reference voltage as the predetermined voltage.

3. The system according to claim 1 wherein

said actuating means is protection release means for releasing a protection circuit of the car stereo.

4. The antitheft system according to claim 1 wherein said detector means comprises a comparator and a memory storing a reference voltage as the predetermined voltage.

5. The antitheft system according to claim 1 wherein said actuating means is protection release means for releasing a protection circuit of the car stereo.

6. An antitheft system for a car stereo to which an original grille is to be attached, the original grille having operating switches for selecting operating modes of the car stereo and a resistor, the antitheft system comprising:

a voltage supply circuit provided in the body of the car stereo;

an identification resistor provided in the body of the car stereo;

circuit means forming a circuit including the voltage supply circuit, the identification resistor and the resistor in the grille when the grille is attached to the body of the car stereo;

the resistance of the identification resistor being set to a value corresponding to the resistance of the resistor of the original grille so that a predetermined voltage is produced across the identification resistor when the grille is attached to the car stereo body;

detector means for detecting the voltage across the identification resistor and for producing a coincident signal when the detected voltage is equal to the predetermined voltage; and

actuating means responsive to the coincident signal for rendering the car stereo operative.