Keyswitch with hysteresis
First Claim
1. In a keyboard wherein the mechanical travel of a key monotonically modulates the amplitude of a signal transmitted according to a first transfer function of p volts per inch of travel to a signal sensor having an electronic hysteresis such that separation between the make and break sensing is m volts, the method of increasing the amount of mechanical travel required of the key to change the amplitude of the signal transmitted by m volts comprising the steps of changing the signal amplitude modulation by the key according to a second transfer function similar to the first transfer function but of q volts per inch of travel, where q is less than p, and of adding a constant direct voltage to the transmitted signal.
2 Assignments
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Accused Products
Abstract
In a keyboard there are a plurality of key operated variable capacitor switches acting as differentiators to change the widths of electrical pulses which are then integrated to give signals whose level indicate which switches have been operated. The gain and operating points of amplifiers can be changed to change the transfer function of the electronics and thus increase the mechanical hysteresis of the switches.
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Citations
10 Claims
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1. In a keyboard wherein the mechanical travel of a key monotonically modulates the amplitude of a signal transmitted according to a first transfer function of p volts per inch of travel to a signal sensor having an electronic hysteresis such that separation between the make and break sensing is m volts, the method of increasing the amount of mechanical travel required of the key to change the amplitude of the signal transmitted by m volts comprising the steps of changing the signal amplitude modulation by the key according to a second transfer function similar to the first transfer function but of q volts per inch of travel, where q is less than p, and of adding a constant direct voltage to the transmitted signal.
- 2. The method of controlling the transfer of signals by means of the travel of a key switch between first and second points along a path, said first and second points being associated with first and second signal amplitudes respectively, said method comprising the steps of periodically generating packets of pulses of given duration, monotonically and continuously changing the duration of the pulses in accordance with the monotonically and continuously changing of the position of the key switch along the path, generating a signal having said first and second amplitudes whose amplitude is a function of the changed durations of the pulses, and sensing for the first and second amplitudes of the generated signal associated with the first and second points, respectively.
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5. Capacitive key switch assemblage comprising:
- a source of packets of electrical pulses, each of the pulses in the packet being of a fixed given duration;
an electrical signal differentiator means, including a resistor and a controllably variable capacitor connected to a keystem and having an input connected to said source and an output, for transmitting from said output for each pulse received at said input a pulse having a duration which is a function of the travel of the keystem; and
a sample and hold electrical signal integrator means, connected to the output of said electrical signal differentiator means, for emitting an integrated signal whose amplitude is a function of the durations of the pulses received from said electrical signal differentiating means. - View Dependent Claims (6, 7, 8)
- a source of packets of electrical pulses, each of the pulses in the packet being of a fixed given duration;
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9. Capacitive key switch assemblage comprising:
- a source of packets of electrical pulses, each of the pulses in the packet being of a fixed duration;
an electrical signal differentiator means, including a resistor and a controllably variable capacitor connected to a keystem and having an input connected to said source and an output for transmitting from said output for each pulse received at said input a pulse having a trailing edge whose slope is a function of the travel of the keystem;
a threshold amplifier means having an input connected to the output of said differentiator means and an output, said threshold amplifier means accepting those portions of each pulse with a variable trailing edge which fall between two signal levels whereby a pulse is transmitted from the output of said threshold amplifier means having a width which is a function of the trailing edge of the pulse received from said differentiating means; and
a sample and hold electrical signal integrator means connected to the output of said threshold amplifier means, for emitting an integrated signal whose amplitude is a function of the duration of the signals emitted by said threshold amplifier means. - View Dependent Claims (10)
- a source of packets of electrical pulses, each of the pulses in the packet being of a fixed duration;
Specification