Security enabling and switching devices

Details Security enabling and switching devices Security enabling and switching devices

1994-12-15

1997-10-14

Hofsass, Jeffery

Communications: electrical

Land vehicle alarms or indicators

Of burglary or unauthorized use

3404255, 340428, 307 102, 307 103, 307 104, 307 105, 180287, B60R 2510

Patent

active

056776632

DESCRIPTION:

BRIEF SUMMARY
1. Field of the Invention
This invention relates in general to security enabling and switching devices for a vehicle having an electrical power supply system. The invention also relates to the enabling and switching devices when used in combination, to a vehicle when fitted with such devices, and to a vehicle component incorporating the switching device. The invention relates more particularly to security devices of the "immobilization" type where the enabling device is an electronic "key" bearing an authorization code and the switching device switches on a vital component of the vehicle (say, the fuel pump (or fuel injection system) or starter motor solenoid) only when activated by a key bearing the correct authorization code.
2. Background of the Invention
It is already known from Australian Patent Application No. 58047/90 to provide a security device to prevent unauthorized usage of a vehicle. The security device comprises an electronic key in which is stored an authorization code, a decoder for receiving the code upon electronic connection of the Key, and an electronic switch to enable operation of a component of the vehicle when the key supplies a valid code to the decoder. Dedicated wiring is provided to transmit the decoded signal from the decoder to the switch when the key is directly electrically connected to the decoder.
This arrangement suffers from several disadvantages associated with the use of this dedicated wiring link. Most importantly, a thief can determine the location of the switch by tracing the wiring from the decoder to the switch. Once located, the switch can be overridden and the vehicle can be stolen. Also, fitting of the wiring can be time-consuming and expensive.
Another vehicle disabling device is described in U.S. Pat. No. 4,463,340 (ADKINS). This device has a permanently connected keyboard. Data from the Keyboard is transmitted to a receiver or switch, using a pulse width modulation (PWM) technique. This system of data transmission was found to be acceptable for words having a low number of bits in their length. However, as word lengths became longer, in order to enhance security, because clock rates at the key (encoder) and receiver (decoder) may differ synchronization can become difficult. This could lead to corruption of data and/or non recognition, by the decoder, of a valid authorization signal.
International Patent Application WO-A-8103002 (BLAIS AUTOSECURITY CORP) describes a coded engine starter system. A modulated carrier signal transmits data to a decoder which decodes the signal and permits a starter motor to be started if the signal is bona fide.
German Patent DE-A-2 503 266 (SVENSKA) teaches a vehicle specific signal source/code generator which imposes its code only on the ignition circuit, and specifically isolates this from the rest of the vehicle's power supply by the use of a filter.
U.S. Pat. No. 4,288,778 (ZUCKER) describes a removable digital encoder which mates with a dedicated socket mounted in an accessible location on the vehicle. The socket has a connection to carry data from the encoder to decoder.
Finally U.S. Pat. No. 4,050,063 (SCHULL) describes a vehicle security system having a mechanical-electronic key which is inserted into a lock system. Upon sequential mechanical and electronic unlocking the security system is immobilized and the vehicle may be driven.
Some of the arrangements described above suffer from the same disadvantages as the device described in the above mentioned Australian Patent Application. Others are complex and/or expensive and may be relatively easily wired around or bypassed.


SUMMARY OF THE INVENTION

According to the present invention there is provided a removable security device for a vehicle, the device having means for receiving a power supply and means for modifying a characteristic of the supply so as to impart an identification signal to said power supply, a characteristic of which signal is received and read to verify a user's authority and which on verification enables the vehicle to be driven.
Preferably verifica

REFERENCES:
patent: 3953831 (1976-04-01), Estrada
patent: 4050063 (1977-09-01), Schull
patent: 4288778 (1981-09-01), Zucker
patent: 4463340 (1984-07-01), Adkins et al.
patent: 5079436 (1992-01-01), Elkins
patent: 5258741 (1993-11-01), Fuller
patent: 5404129 (1995-04-01), Novak et al.
patent: 5469151 (1995-11-01), Lavelle et al.

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