Coded key system using pulse polarity

Claim 2

A key for contactless coded key system comprising a key housing, a circuit disposed in the housing having a memory which may be read from and/or written to, means enabling the memory to be read from and/or written to, means comprising a winding forming part of a transformer for enabling the circuit to be powered from externally of the key and means also comprising the said transformer winding for enabling information to be transmitted to and/or from the key from and/or to another part of the system, and rectifier means connected to the winding such that both positive and negative pulses appearing on the winding are rectified to provide power for the circuit and such that positive and negative pulses can be distinguished form each other to provide operational information to the key, said positive pulses defining a set of positive pulses, said negative pulses defining a set of negative pulses, the pulses of one of said sets of pulses being employed as clock pulses to clock data into the key and the pulses of the other one of said sets of pulses being used to provide the data so clocked.

Claim 3

A key terminal for a contactless coded key system comprising means for accepting a key introduced to the terminal, means comprising a winding forming part of a transformer for transmitting information to and/or receiving information from the key and means also comprising the said transformer winding for transmitting power to the key to power the key, and a microprocessor connected to the transformer winding for controlling the transmission of information by both positive and negative pulses via the winding to the key, said positive pulses defining a set of positive pulses, said negative pulses defining a set of negative pulses, the pulses of one of said sets of pulses being employed as clock pulses to clock data into the key and the pulses of the other one of said sets of pulses being used to provide the data so clocked.

Claim 4

A key terminal for a contactless coded key system comprising means for accepting a key introduced to the terminal, means comprising a winding forming part of a transformer for transmitting information to and/or receiving information from the key and means also comprising the said transformer winding for transmitting power to the key to power the key, and a microprocessor connected to the transformer winding for controlling the transmission of information by both positive and negative pulses via the winding to the key, said positive pulses defining a set of positive pulses, said negative pulses defining a set of negative pulses, the pulses of one of said sets of pulses being employed as clock pulses to clock data into the key and the pulses of the other one of said sets of pulses being used to provide the data so clocked.

Claim 5

A contactless coded key system comprising a key and a key terminal each having a housing and circuitry disposed in the housing, the housing of the terminal being adapted to accept the housing of the key, in which the circuitry in the key housing has a memory which may be read from and/or written to be the circuitry in the terminal, means enabling the memory in the key to be read from and/or written to by the circuit in the terminal, means comprising a winding forming part of a transformer for enabling the circuitry in the key housing to be powered from the terminal, and means also comprising the said transformer winding enabling information to be transmitted to and/or from the key from and/or to the terminal and rectifier means connected to the winding such that both positive and negative pulses appearing on the winding are rectified to provide power for the circuit and such that positive and negative pulses can be distinguished from each other to provide operational information to the key, said positive pulses defining a set of positive pulses, said negative pulses defining a set of negative pulses, the pulses of one of said sets of pulses being employed as clock pulses to clock data into the key and the pulses of the other one of said sets of pulses being used to provide the data so clocked, and in which the circuitry in the terminal has means for transmitting information to and/or receiving information from the key, means for transmitting power to the key to power the key and means to display information received from and/or transmitted to the key and a microprocessor connected to the transformer winding for controlling the transmission of information via the winding to the key.

Claim 6

A contactless coded key system comprising a key and a key terminal each having a housing and circuitry disposed in the housing, the housing of the terminal being adapted to accept the housing of the key, in which the circuitry in the key housing has a memory which may be read from and/or written to be the circuitry in the terminal, means enabling the memory in the key to be read from and/or written to by the circuit in the terminal, means comprising a winding forming part of a transformer for enabling the circuitry in the key housing to be powered from the terminal, and means also comprising the said transformer winding enabling information to be transmitted to and/or from the key from and/or to the terminal and rectifier means connected to the winding such that both positive and negative pulses appearing on the winding are rectified to provide power for the circuit and such that positive and negative pulses can be distinguished from each other to provide operational information to the key, said positive pulses defining a set of positive pulses, said negative pulses defining a set of negative pulses, the pulses of one of said sets of pulses being employed as clock pulses to clock data into the key and the pulses of the other one of said sets of pulses being used to provide the data so clocked, and in which the circuitry in the terminal has means for transmitting information to and/or receiving information from the key, means for transmitting power to the key to power the key and means to display information received from and/or transmitted to the key and a microprocessor connected to the transformer winding for controlling the transmission of information via the winding to the key.

Claim 7

A key as claimed in claim 1, which is moulded from synthetic plastics material.

Claim 8

A terminal as claimed in claim 2, which is moulded from synthetic plastics material.

Claim 9

A key as claimed in claim 1, in which the memory comprises an electrically erasable programmable read only memory.

Claim 10

A key as claimed in claim 6, in which the means enabling the memory to be read from and/or written to comprises an interface circuit.

Claim 11

A key as claimed in claim 1, in which the means enabling information to be transmitted to and/or from the key comprises the winding and a signal producing device.

Claim 12

A key as claimed in claim 8, in which the signal producing device is optical.

Claim 13

A key as claimed in claim 8, in which the signal producing device is electrical.

Claim 14

A key as claimed in claim 9, in which the optical device is a light emitting diode.

Claim 15

A key as claimed in claim 9, in which the optical device is disposed in one end thereof.

Claim 16

A key terminal as claimed in claim 2, in which the terminal comprises means to display information.

Claim 17

A key terminal as claimed in claim 2, comprising means to sense the presence of a key.

Claim 18

A key terminal as claimed in claim 14, in which the means to sense the presence of a key comprises an optical transmitter and an optical receiver so arranged that an inserted key is interposed between transmitter and receiver.

Claim 19

A key terminal as claimed in claim 15, in which the optical transmitter is alight emitting diode and the optical receiver is a phototransistor.