Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
90 words
A cardiac pacemaker of trie Kind having means τor sensing heart activity and means responsive to the sensing means for affecting the operation of said pacemaker, comprising means for establishing a reference level signal representative of the level of sensed extraneous repetitive noise, means for providing a second signal differing from said reference level signal by an amount representative of sensed heart activity, detecting means responsive to said signals to produce an output signal indicative of sensed heart activity, and means for selectively altering the sensitivity of said detecting means.
Claim 2
Dependent Claim
90 words
A cardiac pacemaker of trie Kind having means τor sensing heart activity and means responsive to the sensing means for affecting the operation of said pacemaker, comprising means for establishing a reference level signal representative of the level of sensed extraneous repetitive noise, means for providing a second signal differing from said reference level signal by an amount representative of sensed heart activity, detecting means responsive to said signals to produce an output signal indicative of sensed heart activity, and means for selectively altering the sensitivity of said detecting means.
Claim 3
Dependent Claim
22 words
A pacemaker as claimed in claim 1 wherein said altering means comprises means for establishing one of a predetermined plurality of sensitivities.
Claim 4
Dependent Claim
24 words
A pacemaker as claimed in claim 1 or 2 wherein said detecting means comprises means differentially responsive to said reference level and second signals.
Claim 5
Dependent Claim
31 words
A pacemaker as claimed in claim 3 wherein said detecting means comprises a differential amplifier, said altering means comprising means biassing said differential amplifier and capable of selectively altering the bias.
Claim 6
Dependent Claim
25 words
A pacemaker as claimed in claim 4 wherein said biassing means comprises resistance means and means for establishing a voltage drop across said resistance means.
Claim 7
Dependent Claim
17 words
A pacemaker as claimed in claim 5 wherein said voltage drop establishing means comprise current sink means.
Claim 8
Dependent Claim
20 words
A pacemaker as claimed in claim 6 wherein said current sink means comprises a plurality of selectively conducting current sinks.
Claim 9
Dependent Claim
58 words
A pacemaker as claimed in any preceding claim wherein said altering means is responsive to a sensitivity input having either no signal or a high or low voltage signal and is arranged to provide one of three sensitivities in accordance with the state of the input, the sensitivity in the no-signal state being intermediate the other two sensitivities.
Claim 10
Dependent Claim
71 words
9, A pacemaker as claimed in claims 7 and 8 including at least two current sinks arranged to be conductive when said input is in the no-signal state, at least one of said current sinks being arranged to be turned off when the input is in one of the voltage signal states, and including at least one further current sink arranged to be turned on in the other voltage signal state,
Claim 11
Dependent Claim
30 words
A pacemaker as claimed in any preceding claim wherein said detecting means comprises means providing positive feedback to enhance the production of an output signal indicative of sensed heart activity.
Claim 12
Dependent Claim
35 words
A pacemaker as claimed in claims 9 and 10 wherein said biassing means is arranged to increase the sensitivity of the differential amplifier during the generation of an output signal indicative of sensed heart activity,