Claims
- 1. An apparatus to limit an electrical current in a spur circuit comprising a first spur conductor and a second spur conductor connected to a home run of a field bus network, said apparatus comprising:(a) a first transistor connected to vary an impedance of said first spur conductor in response to a voltage differential between a gate of said first transistor and said second spur conductor; and (b) a second transistor connected to vary said voltage differential in response to said current in said first spur conductor.
- 2. The apparatus of claim 1 further comprising an indicator responsive to said voltage differential to indicate an electrical current in said first spur conductor exceeding a nominal current.
- 3. An apparatus to limit an electrical current in a circuit including a first conductor at a first electrical potential and a second conductor at a different potential, said apparatus comprising:(a) a first transistor connected to vary an impedance of said first conductor in response to a potential at a gate of said first transistor, said gate conductively connected to said second conductor; and (b) a second transistor having a first and a second connection to said first conductor and a third connection to said gate of said first transistor; said second transistor varying said potential at said gate of said first transistor in response to a voltage differential between said first and said second connections.
- 4. The apparatus of claim 3 further comprising a device emitting a signal in response to said potential at said gate of said first transistor.
- 5. The apparatus of claim 4 wherein said device emitting a signal in response to said potential at said gate of said first transistor comprises a light emitting diode.
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a continuation of application Ser. No. 09/344,408, filed Jun. 24, 1999.
US Referenced Citations (8)
Continuations (1)
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Number |
Date |
Country |
Parent |
09/344408 |
Jun 1999 |
US |
Child |
09/771152 |
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US |