Bed egress alarm circuit
AssigneeWilliam Beaumont Hospital
InventorsKenneth J. Cook, Norman H. Horwitz
Life of this patent
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Abstract
A condition responsive circuit for generating an output signal upon the opening of a switch. An FET draws nominal current when the switch is closed. When the switch is opened the FET conducts to generate an output. The output may include an audio alarm, an oscillator and a transmitter to generate an alarm at a distant location, or a visual indicator.
Claims10
A condition responsive circuit for signalling the departure of a patient from a bed or the like by generating an output signal upon the opening of a switch, comprising:
- a switch being normally closed by the weight of a patient in a bed;
- an FET having source, drain and gate electrodes, said gate electrode connected to said switch for normally drawing only a nominal current and for continuously biasing said gate electrode to render said FET non-conductive;
- a normally off output means coupled to said at least one of said source and drain electrodes for generating an output signal when said FET is rendered conductive;
- the opening of said switch to remove the continuous bias from said gate electrode;
- delay means coupled to said switch and said gate electrode for maintaining a bias at said gate electrode to prevent said FET from being rendered conductive for a predetermined time interval after the opening of said switch;
- and
- said output means including an SCR, an SCR switch, and a signal means, all connected in series;
- said SCR being rendered conductive by said FET being rendered conductive to thereby generate an output signal from said signal means, and said SCR being thereafter rendered non-conductive only by operating said SCR switch.
A condition responsive circuit for signalling the departure of a patient from a bed or the like by generating an output signal upon the opening of a switch, comprising:
- a switch being normally closed by the weight of a patient in a bed;
- an FET having source, drain and gate electrodes, said gate electrode connected to said switch for normally drawing only a nominal current and for continuously biasing said gate electrode to render said FET non-conductive;
- a normally off output means coupled to at least one of said source and drain electrodes for generating an output signal when said FET is rendered conductive;
- the opening of said switch to remove the continuous bias from said gate electrode;
- and
- delay means coupled to said switch and said gate electrode for maintaining a bias at said gate electrode to prevent said FET from being rendered conductive for a predetermined time interval after the opening of said switch.
The circuit of claim [1] 2 and further including:
- second switch means connected in series with said normally closed switch for testing the operation of said circuit by removing said continuous bias from the FET gate.
The circuit of claim [1] 2 wherein said output means includes a normally non-conductive electronic switch rendered conductive when said FET is rendered conductive.
The circuit of claim [1] 2 wherein said switch is pressure sensitive.
The circuit of claim [1] 2 wherein said output means includes an audio alarm.
Dependencies are inferred from the claim text.