Communications: electrical – Continuously variable indicating – With meter reading
Patent
1991-03-15
1993-10-12
Yusko, Donald J.
Communications: electrical
Continuously variable indicating
With meter reading
34082531, 34082534, H04Q 100
Patent
active
052529657
ABSTRACT:
A system for unlocking any of several vehicles by a passive electronic key coupled to base units in the vehicles by a radio link uses short range LF transmission for signals to the key and VHF transmission for signals to the base units. The key has a ferrite antenna connected to a receiver comprising a comparator. When an operator pulls the door handle, codes stored in the base are transmitted to identify any authorized key within the range. The key has a memory partitioned into separate blocks for different base units and another block for a scratchpad memory. A state machine stores the block addresses and controls access to the blocks according to the transmitted codes. When a block is accessed, a secure ID in the block is sent to the base unit to verify that the key is authorized to unlock the vehicle. The ID can be updated upon command from the base unit using the same codes to assure that an authorized unit is receiving the new ID. The new ID is written to the scratchpad, verified for correctness, and the scratchpad address is exchanged for the address of the block containing the old ID. Auxiliary data specific to the vehicle or to the user of the electronic key may also be stored in the memory blocks and retrieved along with the ID.
REFERENCES:
patent: 4163215 (1979-07-01), Iida
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patent: 4829296 (1989-05-01), Clark et al.
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patent: 4973958 (1990-11-01), Hirano
Campbell Kenneth R.
Gidwani Sachal B.
Slone Eric L.
Delco Electronics Corporation
Sigler Robert M.
Yusko Donald J.
Zimmerman Brian
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