An active device for a coded information arrangement, a method of supplying coded information thereto, and systems comprising such an active device

Claim 3

A method according to claim 1, wherein the uncoded signal is also supplied to a programming unit which supplies said signals to the second input circuit (41) at said respective times.

Claim 4

A method according to claim 2 wherein the logic signal (W) is derived in the active device from the first input circuit by frequency division, and the programming unit includes means duplicating the frequency division means of the active device to determine said respective times.

Claim 5

An active device having first (21) and second (41) input circuits, a frequency division circuit (134) connected to the first input circuit, and a memory (31), the second input circuit being connected to a clock input of the memory, characterised in that an output (W) of the frequency division circuit is connected to a coding input of the memory.

Claim 6

An active device having first (21) and second (41) input circuits, a frequency division circuit (134) connected to the first input circuit, and a memory (31), the second input circuit being connected to a clock input of the memory, characterised in that an output (W) of the frequency division circuit is connected to a coding input of the memory.

Claim 7

An active device according to claim 4 wherein the output (W) is from an intermediate part of the frequency division circuit (134).

Claim 8

An active device according to claim 4 or 5 comprising a memory protection circuit (410) for preventing undesired changing of the coded information stored in the memory, the memory protection circuit being connected to the second input circuit 41, wherein, when it is desired to change the stored information, a predetermined series of pulses must be applied via the second input circuit to the memory protection circuit and wherein the memory protection circuit includes means (42, 45, 171 - 178) for comparing both the number and the timing of pulses actually applied to the second input circuit with the number and the timing of the predetermined series.

Claim 9

An active device according to claim 6, wherein logic means (171) of the memory protection circuit (410) are connected to selected points of the frequency division circuit (134) whereby to determine said predetermined series.

Claim 10

An active device according to any of the claims 4 to 7, wherein the division ratio of the frequency division circuit (134) is adjustable.

Claim 11

An active device according to any of claims 4 to 8 wherein the first and second input circuits have a single input for receiving modulated signals, and the second input circuit is connected to the input via a demodulator (250) .

Claim 12

An active device according to any of claims 4 to 9 comprising data means (161; 162; BO-B7) for supplying further information independently of the memory (31).

Claim 13

An active device according to claim 10, wherein the outputs of the memory and the data means are connected to corresponding inputs of data selector means, (32;163) .

Claim 14

An active device according to claim 10 or 11, said data means comprising one or more input connections (BO-B7) connected to means for providing signals representing the updated values of one or more parameters, said values constituting said further information.

Claim 15

An active device according to claim 11 and 12 wherein said input connections are connected to respective inputs of said data selector means (32) via respective further data selector means, (310 - 317) said further data selector means also being connected to respective outputs (DO - D7) of the memory, and select input means (319) being provided for said further data selector means whereby said inputs of said first mentioned data selector means (32) receive information either from said input connections or from said respective outputs of the memory.

Claim 16

An active device according to any of claims 10 to 13 comprising a battery, wherein said further information relates to the battery voltage level.

Claim 17

An active device according to claim 14 comprising means (161) for detecting that the battery voltage has fallen below a predetermined level and altering a part of said further information.

Claim 18

An active device according to claim 14 comprising means (162) for detecting that the battery voltage has fallen below a predetermined level and means, (163) connected to said detecting means, for preventing coded information in the memory from being transmitted.

Claim 19

An active device according to any of claims 14 to 16 comprising first means (161) for detecting that the battery voltage has fallen below a first predetermined level and second means (162) for detecting that the battery voltage has fallen below a second predetermined level, said second level being lower than said first level.

Claim 21

A system according to claim 18 wherein the frequency division means duplicates the frequency division circuit (134) of the active device.

Claim 22

A coded information detecting system comprising: (i) a plurality of active devices according to any of claims 4 to 17, each comprising a receiver, and a a transmitter for transmitting in response to an input signal received by the receiver an output signal includingthe contents of the memory (31), (ii) an interrogator unit (210) which is arranged to provide said input signal and detect said output signal, and which includes decoding means, (223) and (iii) a polling unit (211) which is arranged to supply said input signal from said interrogator unit successively to each one of a plurality of aerial units (231 - 234) at separate sites, and to return any received output signal from a transponder to the interrogator unit, wherein the decoding means includes means for detecting whether an initial transponder output signal is received from an aerial unit and means responsive to said detecting means which, in the presence of a transponder output signal, allows the polling unit to supply the coded information from the memory of the transponder to the interrogator unit and which, in the absence of a transponder output signal, instructs the polling unit to skip immediately to the next aerial unit.