Keyboard arrangements

Claim 2

A keyboard arrangement comprising a plurality of keys and means for detecting operation of the keys of said plurality, characterised by said means (2) being operative in response to a first condition to detect operation of any of said keys (11,12) of said plurality and being operative in response to a second condition to detect operation only of any keys (12) in a restricted set of said plurality of keys.

Claim 3

A keyboard arrangement as claimed in Claim 1 further characterised in that in said first condition a signal has a first value and in said second condition the signal has a second value.

Claim 4

A keyboard arrangement as claimed in Claim 2 further characterised in that the signal is derived from power output of a first power source (14), the signal having the first value in response to the first power source (14) being operative to produce the power output and the signal having the second value in response to the first power source (14) being inoperative.

Claim 5

A keyboard arrangement as claimed in Claim 3 absence of power output from the first power source(14).

Claim 6

A keyboard arrangement as claimed in Claim 1 or 2 further characterised by the provision of means selectively operable to produce said first and second conditions.

Claim 7

A keyboard arrangement as claimed in Claim 5 further characterised in that said selectively operable means comprises a key-operated switch.

Claim 8

A keyboard arrangement as claimed in Claim 4 further characterised by the provision of first scanning means (37) operative to scan and detect operation of any of said plurality of keys (11) excluding said restricted set of keys (12) and second scanning means (20) operative to scan and detect operation of the keys of said restricted set.

Claim 9

A keyboard arrangement as claimed in Claim 7 further characterised in that the first power source (14) is connected to supply power to energise both said first and second scanning means (37,20) and said second power source (15) is connected to supply power to energise said second scanning means (20), whereby the first scanning means (37) is not energised when the first power source (14) is in- characterised in that the means for detecting operation of keys comprises a first set of conductors (33,34), a second set of conductors (35), each key (11,12) being arranged when operated to cause a short-circuit between a conductor (33,34) of the first set and a conductor (35) of the second set, and control means (37,20) for applying a scanning signal to selected ones of the first set of conductors (33,34), which means (37,20) in response to the first condition applies the scanning signal to each in turn of the conductors of the first set (33,34) and in response to the second condition applies the scanning signal only to the conductor (if one) or each in turn (if more than one) of the conductors (34) in a restricted sub set of the first set of conductors, which subset consists of the or each conductor of the first set which in operation of any key (12) of the said restricted set of keys is short-circuited to a conductor of the second set, and means for detecting any short circuit between the conductor of the first set to which a scanning signal is applied and any conductor of the second set.

Claim 10

A keyboard arrangement as claimed in Claim 9 outputs from a shift register (37).

Claim 11

Apparatus including a keyboard arrangement as claimed in any previous Claim which apparatus performs a set of functions in response to depression of keys of the keyboard, characterised in that the functions performed in response to depression only of keys (12) in the restricted set of keys being a restricted but useful subset of the whole.

Claim 12

Apparatus as claimed in Claim 11 providing data processing and telephony functions further characterised in that keys (11,12) of the plurality are operable for effecting data processing functions and only keys (12) of the restricted set of keys are operable for effecting telephony functions.